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<!DOCTYPE html> <html> <!-- Created by GNU Texinfo 7.1, https://www.gnu.org/software/texinfo/ --> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>bc Command Manual</title> <meta name="description" content="bc Command Manual"> <meta name="keywords" content="bc Command Manual"> <meta name="resource-type" content="document"> <meta name="distribution" content="global"> <meta name="Generator" content="makeinfo"> <meta name="viewport" content="width=device-width,initial-scale=1"> <link href="#Top" rel="start" title="Top"> <link href="#SEC_Contents" rel="contents" title="Table of Contents"> <link href="dir.html#Top" rel="up" title="(dir)"> <link href="#Introduction" rel="next" title="Introduction"> <link href="dir.html#Top" rel="prev" title="(dir)"> <style type="text/css"> <!-- a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em} div.example {margin-left: 3.2em} span:hover a.copiable-link {visibility: visible} --> </style> </head> <body lang="en"> <a class="node-id" id="Top"></a><div class="nav-panel"> <p> Next: <a href="#Introduction" accesskey="n" rel="next">Introduction</a>, Previous: <a href="dir.html#Top" accesskey="p" rel="prev">(dir)</a>, Up: <a href="dir.html#Top" accesskey="u" rel="up">(dir)</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h1 class="node"><span>Top<a class="copiable-link" href="#Top"> ¶</a></span></h1> <hr> <div class="chapter-level-extent" id="Introduction"> <div class="nav-panel"> <p> Next: <a href="#Basic-Elements" accesskey="n" rel="next">Basic Elements</a>, Previous: <a href="#Top" accesskey="p" rel="prev">Top</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h2 class="chapter" id="Introduction-1"><span>1 Introduction<a class="copiable-link" href="#Introduction-1"> ¶</a></span></h2> <ul class="mini-toc"> <li><a href="#Description" accesskey="1">Description</a></li> <li><a href="#Command-Line-Options" accesskey="2">Command Line Options</a></li> </ul> <hr> <div class="section-level-extent" id="Description"> <div class="nav-panel"> <p> Next: <a href="#Command-Line-Options" accesskey="n" rel="next">Command Line Options</a>, Previous: <a href="#Introduction" accesskey="p" rel="prev">Introduction</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Description-1"><span>1.1 Description<a class="copiable-link" href="#Description-1"> ¶</a></span></h3> <p><code class="command">bc</code> [ -hlwsqv ] [long-options] [ <var class="var"> file ...</var> ] </p> <p><code class="command">bc</code> is a language that supports arbitrary precision numbers with interactive execution of statements. There are some similarities in the syntax to the C programming language. A standard math library is available by command line option. If requested, the math library is defined before processing any files. <code class="command">bc</code> starts by processing code from all the files listed on the command line in the order listed. After all files have been processed, <code class="command">bc</code> reads from the standard input. All code is executed as it is read. (If a file contains a command to halt the processor, <code class="command">bc</code> will never read from the standard input.) </p> <p>This version of <code class="command">bc</code> contains several extensions beyond traditional <code class="command">bc</code> implementations and the POSIX draft standard. Command line options can cause these extensions to print a warning or to be rejected. This document describes the language accepted by this processor. Extensions will be identified as such. </p> <p>The author would like to thank Steve Sommars (<a class="email" href="mailto:Steve.Sommars@att.com">Steve.Sommars@att.com</a>) for his extensive help in testing the implementation. Many great suggestions were given. This is a much better product due to his involvement. </p> <p>Email bug reports to <a class="email" href="mailto:bug-bc@gnu.org">bug-bc@gnu.org</a>. Be sure to include the word “bc” somewhere in the “Subject:” field. </p> <hr> </div> <div class="section-level-extent" id="Command-Line-Options"> <div class="nav-panel"> <p> Next: <a href="#Numbers" accesskey="n" rel="next">Numbers</a>, Previous: <a href="#Description" accesskey="p" rel="prev">Description</a>, Up: <a href="#Introduction" accesskey="u" rel="up">Introduction</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Command-Line-Options-1"><span>1.2 Command Line Options<a class="copiable-link" href="#Command-Line-Options-1"> ¶</a></span></h3> <p><code class="command">bc</code> takes the following options from the command line: </p><dl class="table"> <dt><code class="code">-h, --help</code></dt> <dd><p>Print the usage and exit. </p> </dd> <dt><code class="code">-l, --mathlib</code></dt> <dd><p>Define the standard math library. </p> </dd> <dt><code class="code">-w, --warn</code></dt> <dd><p>Give warnings for extensions to POSIX <code class="command">bc</code>. </p> </dd> <dt><code class="code">-s, --standard</code></dt> <dd><p>Process exactly the POSIX <code class="command">bc</code> language. </p> </dd> <dt><code class="code">-q, --quiet</code></dt> <dd><p>Do not print the normal GNU <code class="command">bc</code> welcome. </p> </dd> <dt><code class="code">-v, --version</code></dt> <dd><p>Print the version number and copyright and quit. </p> </dd> </dl> <hr> </div> </div> <div class="chapter-level-extent" id="Basic-Elements"> <div class="nav-panel"> <p> Next: <a href="#Expressions" accesskey="n" rel="next">Expressions</a>, Previous: <a href="#Introduction" accesskey="p" rel="prev">Introduction</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h2 class="chapter" id="Basic-Elements-1"><span>2 Basic Elements<a class="copiable-link" href="#Basic-Elements-1"> ¶</a></span></h2> <ul class="mini-toc"> <li><a href="#Numbers" accesskey="1">Numbers</a></li> <li><a href="#Variables" accesskey="2">Variables</a></li> <li><a href="#Comments" accesskey="3">Comments</a></li> </ul> <hr> <div class="section-level-extent" id="Numbers"> <div class="nav-panel"> <p> Next: <a href="#Variables" accesskey="n" rel="next">Variables</a>, Previous: <a href="#Command-Line-Options" accesskey="p" rel="prev">Command Line Options</a>, Up: <a href="#Basic-Elements" accesskey="u" rel="up">Basic Elements</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Numbers-1"><span>2.1 Numbers<a class="copiable-link" href="#Numbers-1"> ¶</a></span></h3> <p>The most basic element in <code class="command">bc</code> is the number. Numbers are arbitrary precision numbers. This precision is both in the integer part and the fractional part. All numbers are represented internally in decimal and all computation is done in decimal. (This version truncates results from divide and multiply operations.) There are two attributes of numbers, the length and the scale. The length is the total number of digits used by <code class="command">bc</code> to represent a number and the scale is the total number of decimal digits after the decimal point. For example, .000001 has a length of 6 and scale of 6, while 1935.000 has a length of 7 and a scale of 3. </p> <hr> </div> <div class="section-level-extent" id="Variables"> <div class="nav-panel"> <p> Next: <a href="#Comments" accesskey="n" rel="next">Comments</a>, Previous: <a href="#Numbers" accesskey="p" rel="prev">Numbers</a>, Up: <a href="#Basic-Elements" accesskey="u" rel="up">Basic Elements</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Variables-1"><span>2.2 Variables<a class="copiable-link" href="#Variables-1"> ¶</a></span></h3> <p>Numbers are stored in two types of variables, simple variables and arrays. Both simple variables and array variables are named. Names begin with a letter followed by any number of letters, digits and underscores. All letters must be lower case. (Full alphanumeric names are an extension. In POSIX <code class="command">bc</code> all names are a single lower case letter.) The type of variable is clear by the context because all array variable names will be followed by brackets ( [ ] ). </p> <p>There are four special variables, <var class="var">scale</var>, <var class="var">ibase</var>, <var class="var">obase</var>, and <var class="var">last</var>. <var class="var">scale</var> defines how some operations use digits after the decimal point. The default value of <var class="var">scale</var> is 0. <var class="var">ibase</var> and <var class="var">obase</var> define the conversion base for input and output numbers. The default for both input and output is base 10. <var class="var">last</var> (an extension) is a variable that has the value of the last printed number. These will be discussed in further detail where appropriate. All of these variables may have values assigned to them as well as used in expressions. </p> <hr> </div> <div class="section-level-extent" id="Comments"> <div class="nav-panel"> <p> Previous: <a href="#Variables" accesskey="p" rel="prev">Variables</a>, Up: <a href="#Basic-Elements" accesskey="u" rel="up">Basic Elements</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Comments-1"><span>2.3 Comments<a class="copiable-link" href="#Comments-1"> ¶</a></span></h3> <p>Comments in <code class="command">bc</code> start with the characters <code class="code">/*</code> and end with the characters <code class="code">*/</code>. Comments may start anywhere and appear as a single space in the input. (This causes comments to delimit other input items. For example, a comment can not be found in the middle of a variable name.) Comments include any newlines (end of line) between the start and the end of the comment. </p> <p>To support the use of scripts for <code class="command">bc</code>, a single line comment has been added as an extension. A single line comment starts at a <code class="code">#</code> character and continues to the next end of the line. The end of line character is not part of the comment and is processed normally. </p> <hr> </div> </div> <div class="chapter-level-extent" id="Expressions"> <div class="nav-panel"> <p> Next: <a href="#Statements" accesskey="n" rel="next">Statements</a>, Previous: <a href="#Basic-Elements" accesskey="p" rel="prev">Basic Elements</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h2 class="chapter" id="Expressions-1"><span>3 Expressions<a class="copiable-link" href="#Expressions-1"> ¶</a></span></h2> <ul class="mini-toc"> <li><a href="#About-Expressions-and-Special-Variables" accesskey="1">About Expressions and Special Variables</a></li> <li><a href="#Basic-Expressions" accesskey="2">Basic Expressions</a></li> <li><a href="#Relational-Expressions" accesskey="3">Relational Expressions</a></li> <li><a href="#Boolean-Expressions" accesskey="4">Boolean Expressions</a></li> <li><a href="#Precedence" accesskey="5">Precedence</a></li> <li><a href="#Special-Expressions" accesskey="6">Special Expressions</a></li> </ul> <hr> <div class="section-level-extent" id="About-Expressions-and-Special-Variables"> <div class="nav-panel"> <p> Next: <a href="#Basic-Expressions" accesskey="n" rel="next">Basic Expressions</a>, Previous: <a href="#Expressions" accesskey="p" rel="prev">Expressions</a>, Up: <a href="#Expressions" accesskey="u" rel="up">Expressions</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="About-Expressions-and-Special-Variables-1"><span>3.1 About Expressions and Special Variables<a class="copiable-link" href="#About-Expressions-and-Special-Variables-1"> ¶</a></span></h3> <p>The numbers are manipulated by expressions and statements. Since the language was designed to be interactive, statements and expressions are executed as soon as possible. There is no main program. Instead, code is executed as it is encountered. (Functions, discussed in detail later, are defined when encountered.) </p> <p>A simple expression is just a constant. <code class="command">bc</code> converts constants into internal decimal numbers using the current input base, specified by the variable <var class="var">ibase</var>. (There is an exception in functions.) The legal values of <var class="var">ibase</var> are 2 through 36. (Bases greater than 16 are an extension.) Assigning a value outside this range to <var class="var">ibase</var> will result in a value of 2 or 36. Input numbers may contain the characters 0-9 and A-Z. (Note: They must be capitals. Lower case letters are variable names.) Single digit numbers always have the value of the digit regardless of the value of <var class="var">ibase</var>. (i.e. A = 10.) For multi-digit numbers, <code class="command">bc</code> changes all input digits greater or equal to <var class="var">ibase</var> to the value of <var class="var">ibase</var>-1. This makes the number <code class="code">ZZZ</code> always be the largest 3 digit number of the input base. </p> <p>Full expressions are similar to many other high level languages. Since there is only one kind of number, there are no rules for mixing types. Instead, there are rules on the scale of expressions. Every expression has a scale. This is derived from the scale of original numbers, the operation performed and in many cases, the value of the variable <var class="var">scale</var>. Legal values of the variable <var class="var">scale</var> are 0 to the maximum number representable by a C integer. </p> <hr> </div> <div class="section-level-extent" id="Basic-Expressions"> <div class="nav-panel"> <p> Next: <a href="#Relational-Expressions" accesskey="n" rel="next">Relational Expressions</a>, Previous: <a href="#About-Expressions-and-Special-Variables" accesskey="p" rel="prev">About Expressions and Special Variables</a>, Up: <a href="#Expressions" accesskey="u" rel="up">Expressions</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Basic-Expressions-1"><span>3.2 Basic Expressions<a class="copiable-link" href="#Basic-Expressions-1"> ¶</a></span></h3> <p>In the following descriptions of legal expressions, "expr" refers to a complete expression and "<var class="var">var</var>" refers to a simple or an array variable. A simple variable is just a </p> <p><var class="var">name</var> </p> <p>and an array variable is specified as </p> <p><var class="var">name</var>[<var class="var">expr</var>] </p> <p>Unless specifically mentioned the scale of the result is the maximum scale of the expressions involved. </p> <dl class="table"> <dt><code class="code">- expr</code></dt> <dd><p>The result is the negation of the expression. </p> </dd> <dt><code class="code">++ <var class="var">var</var></code></dt> <dd><p>The variable is incremented by one and the new value is the result of the expression. </p> </dd> <dt><code class="code">-- <var class="var">var</var></code></dt> <dd><p>The variable is decremented by one and the new value is the result of the expression. </p> </dd> <dt><code class="code"><var class="var">var</var> ++</code></dt> <dd><p>The result of the expression is the value of the variable and then the variable is incremented by one. </p> </dd> <dt><code class="code"><var class="var">var</var> --</code></dt> <dd><p>The result of the expression is the value of the variable and then the variable is decremented by one. </p> </dd> <dt><code class="code">expr + expr</code></dt> <dd><p>The result of the expression is the sum of the two expressions. </p> </dd> <dt><code class="code">expr - expr</code></dt> <dd><p>The result of the expression is the difference of the two expressions. </p> </dd> <dt><code class="code">expr * expr</code></dt> <dd><p>The result of the expression is the product of the two expressions. </p> </dd> <dt><code class="code">expr / expr</code></dt> <dd><p>The result of the expression is the quotient of the two expressions. The scale of the result is the value of the variable <code class="code">scale</code> </p> </dd> <dt><code class="code">expr % expr</code></dt> <dd><p>The result of the expression is the "remainder" and it is computed in the following way. To compute a%b, first a/b is computed to <var class="var">scale</var> digits. That result is used to compute a-(a/b)*b to the scale of the maximum of <var class="var">scale</var>+scale(b) and scale(a). If <var class="var">scale</var> is set to zero and both expressions are integers this expression is the integer remainder function. </p> </dd> <dt><code class="code">expr ^ expr</code></dt> <dd><p>The result of the expression is the value of the first raised to the second. The second expression must be an integer. (If the second expression is not an integer, a warning is generated and the expression is truncated to get an integer value.) The scale of the result is <var class="var">scale</var> if the exponent is negative. If the exponent is positive the scale of the result is the minimum of the scale of the first expression times the value of the exponent and the maximum of <var class="var">scale</var> and the scale of the first expression. (e.g. scale(a^b) = min(scale(a)*b, max(<var class="var">scale</var>, scale(a))).) It should be noted that expr^0 will always return the value of 1. </p> </dd> <dt><code class="code">( expr )</code></dt> <dd><p>This alters the standard precedence to force the evaluation of the expression. </p> </dd> <dt><code class="code"><var class="var">var</var> = expr</code></dt> <dd><p>The variable is assigned the value of the expression. </p> </dd> <dt><code class="code"><var class="var">var</var> <op>= expr</code></dt> <dd><p>This is equivalent to "<var class="var">var</var> = <var class="var">var</var> <op> expr" with the exception that the "<var class="var">var</var>" part is evaluated only once. This can make a difference if "<var class="var">var</var>" is an array. </p></dd> </dl> <hr> </div> <div class="section-level-extent" id="Relational-Expressions"> <div class="nav-panel"> <p> Next: <a href="#Boolean-Expressions" accesskey="n" rel="next">Boolean Expressions</a>, Previous: <a href="#Basic-Expressions" accesskey="p" rel="prev">Basic Expressions</a>, Up: <a href="#Expressions" accesskey="u" rel="up">Expressions</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Relational-Expressions-1"><span>3.3 Relational Expressions<a class="copiable-link" href="#Relational-Expressions-1"> ¶</a></span></h3> <p>Relational expressions are a special kind of expression that always evaluate to 0 or 1, 0 if the relation is false and 1 if the relation is true. These may appear in any legal expression. (POSIX <code class="command">bc</code> requires that relational expressions are used only in <code class="code">if</code>, <code class="code">while</code>, and <code class="code">for</code> statements and that only one relational test may be done in them.) The relational operators are </p> <dl class="table"> <dt><code class="code">expr1 < expr2</code></dt> <dd><p>The result is 1 if expr1 is strictly less than expr2. </p> </dd> <dt><code class="code">expr1 <= expr2</code></dt> <dd><p>The result is 1 if expr1 is less than or equal to expr2. </p> </dd> <dt><code class="code">expr1 > expr2</code></dt> <dd><p>The result is 1 if expr1 is strictly greater than expr2. </p> </dd> <dt><code class="code">expr1 >= expr2</code></dt> <dd><p>The result is 1 if expr1 is greater than or equal to expr2. </p> </dd> <dt><code class="code">expr1 == expr2</code></dt> <dd><p>The result is 1 if expr1 is equal to expr2. </p> </dd> <dt><code class="code">expr1 != expr2</code></dt> <dd><p>The result is 1 if expr1 is not equal to expr2. </p></dd> </dl> <hr> </div> <div class="section-level-extent" id="Boolean-Expressions"> <div class="nav-panel"> <p> Next: <a href="#Precedence" accesskey="n" rel="next">Precedence</a>, Previous: <a href="#Relational-Expressions" accesskey="p" rel="prev">Relational Expressions</a>, Up: <a href="#Expressions" accesskey="u" rel="up">Expressions</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Boolean-Expressions-1"><span>3.4 Boolean Expressions<a class="copiable-link" href="#Boolean-Expressions-1"> ¶</a></span></h3> <p>Boolean operations are also legal. (POSIX <code class="command">bc</code> does NOT have boolean operations). The result of all boolean operations are 0 and 1 (for false and true) as in relational expressions. The boolean operators are: </p> <dl class="table"> <dt><code class="code">!expr</code></dt> <dd><p>The result is 1 if expr is 0. </p> </dd> <dt><code class="code">expr && expr</code></dt> <dd><p>The result is 1 if both expressions are non-zero. </p> </dd> <dt><code class="code">expr || expr</code></dt> <dd><p>The result is 1 if either expression is non-zero. </p></dd> </dl> <hr> </div> <div class="section-level-extent" id="Precedence"> <div class="nav-panel"> <p> Next: <a href="#Special-Expressions" accesskey="n" rel="next">Special Expressions</a>, Previous: <a href="#Boolean-Expressions" accesskey="p" rel="prev">Boolean Expressions</a>, Up: <a href="#Expressions" accesskey="u" rel="up">Expressions</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Precedence-1"><span>3.5 Precedence<a class="copiable-link" href="#Precedence-1"> ¶</a></span></h3> <p>The expression precedence is as follows: (lowest to highest) </p> <div class="example"> <pre class="example-preformatted">|| operator, left associative && operator, left associative ! operator, nonassociative Relational operators, left associative Assignment operator, right associative + and - operators, left associative *, / and % operators, left associative ^ operator, right associative unary - operator, nonassociative ++ and -- operators, nonassociative </pre></div> <p>This precedence was chosen so that POSIX compliant <code class="command">bc</code> programs will run correctly. This will cause the use of the relational and logical operators to have some unusual behavior when used with assignment expressions. Consider the expression: </p> <div class="example"> <pre class="example-preformatted">a = 3 < 5 </pre></div> <p>Most C programmers would assume this would assign the result of "3 < 5" (the value 1) to the variable "a". What this does in <code class="command">bc</code> is assign the value 3 to the variable "a" and then compare 3 to 5. It is best to use parentheses when using relational and logical operators with the assignment operators. </p> <hr> </div> <div class="section-level-extent" id="Special-Expressions"> <div class="nav-panel"> <p> Previous: <a href="#Precedence" accesskey="p" rel="prev">Precedence</a>, Up: <a href="#Expressions" accesskey="u" rel="up">Expressions</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Special-Expressions-1"><span>3.6 Special Expressions<a class="copiable-link" href="#Special-Expressions-1"> ¶</a></span></h3> <p>There are a few more special expressions that are provided in <code class="command">bc</code>. These have to do with user-defined functions and standard functions. They all appear as "<var class="var">name</var><code class="code">(</code><var class="var">parameters</var><code class="code">)</code>". See <a class="xref" href="#Functions">Functions</a>, for user-defined functions. The standard functions are: </p> <dl class="table"> <dt><code class="code">length ( <var class="var">expression</var> )</code></dt> <dd><p>The value of the length function is the number of significant digits in the expression. </p> </dd> <dt><code class="code">read ( )</code></dt> <dd><p>The <code class="code">read</code> function (an extension) will read a number from the standard input, regardless of where the function occurs. Beware, this can cause problems with the mixing of data and program in the standard input. The best use for this function is in a previously written program that needs input from the user, but never allows program code to be input from the user. The value of the <code class="code">read</code> function is the number read from the standard input using the current value of the variable <var class="var">ibase</var> for the conversion base. </p> </dd> <dt><code class="code">scale ( <var class="var">expression</var> )</code></dt> <dd><p>The value of the <code class="code">scale</code> function is the number of digits after the decimal point in the expression. </p> </dd> <dt><code class="code">sqrt ( <var class="var">expression</var> )</code></dt> <dd><p>The value of the <code class="code">sqrt</code> function is the square root of the expression. If the expression is negative, a run time error is generated. </p></dd> </dl> <hr> </div> </div> <div class="chapter-level-extent" id="Statements"> <div class="nav-panel"> <p> Next: <a href="#Functions" accesskey="n" rel="next">Functions</a>, Previous: <a href="#Expressions" accesskey="p" rel="prev">Expressions</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h2 class="chapter" id="Statements-1"><span>4 Statements<a class="copiable-link" href="#Statements-1"> ¶</a></span></h2> <p>Statements (as in most algebraic languages) provide the sequencing of expression evaluation. In <code class="command">bc</code> statements are executed "as soon as possible." Execution happens when a newline in encountered and there is one or more complete statements. Due to this immediate execution, newlines are very important in <code class="command">bc</code>. In fact, both a semicolon and a newline are used as statement separators. An improperly placed newline will cause a syntax error. Because newlines are statement separators, it is possible to hide a newline by using the backslash character. The sequence "\<nl>", where <nl> is the newline appears to <code class="command">bc</code> as whitespace instead of a newline. A statement list is a series of statements separated by semicolons and newlines. The following is a list of <code class="command">bc</code> statements and what they do: (Things enclosed in brackets ( [ ] ) are optional parts of the statement.) </p> <dl class="table"> <dt><code class="code"><var class="var">expression</var></code></dt> <dd><p>This statement does one of two things. If the expression starts with "<variable> <assignment> ...", it is considered to be an assignment statement. If the expression is not an assignment statement, the expression is evaluated and printed to the output. After the number is printed, a newline is printed. For example, "a=1" is an assignment statement and "(a=1)" is an expression that has an embedded assignment. All numbers that are printed are printed in the base specified by the variable <var class="var">obase</var>. The legal values for <var class="var">obase</var> are 2 through BC_BASE_MAX (see <a class="pxref" href="#Environment-Variables">Environment Variables</a>). For bases 2 through 16, the usual method of writing numbers is used. For bases greater than 16, <code class="command">bc</code> uses a multi-character digit method of printing the numbers where each higher base digit is printed as a base 10 number. The multi-character digits are separated by spaces. Each digit contains the number of characters required to represent the base ten value of "<var class="var">obase</var> -1". Since numbers are of arbitrary precision, some numbers may not be printable on a single output line. These long numbers will be split across lines using the "\" as the last character on a line. The maximum number of characters printed per line is 70. Due to the interactive nature of <code class="command">bc</code>, printing a number causes the side effect of assigning the printed value to the special variable <var class="var">last</var>. This allows the user to recover the last value printed without having to retype the expression that printed the number. Assigning to <var class="var">last</var> is legal and will overwrite the last printed value with the assigned value. The newly assigned value will remain until the next number is printed or another value is assigned to <var class="var">last</var>. (Some installations may allow the use of a single period (.) which is not part of a number as a short hand notation for for <var class="var">last</var>.) </p> </dd> <dt><code class="code"><var class="var">string</var></code></dt> <dd><p>The string is printed to the output. Strings start with a double quote character and contain all characters until the next double quote character. All characters are taken literally, including any newline. No newline character is printed after the string. </p> </dd> <dt><code class="code">print <var class="var">list</var></code></dt> <dd><p>The <code class="code">print</code> statement (an extension) provides another method of output. The <var class="var">list</var> is a list of strings and expressions separated by commas. Each string or expression is printed in the order of the list. No terminating newline is printed. Expressions are evaluated and their value is printed and assigned to the variable <code class="code">last</code>. Strings in the print statement are printed to the output and may contain special characters. Special characters start with the backslash character (\e). The special characters recognized by <code class="command">bc</code> are "a" (alert or bell), "b" (backspace), "f" (form feed), "n" (newline), "r" (carriage return), "q" (double quote), "t" (tab), and "\e" (backslash). Any other character following the backslash will be ignored. </p> </dd> <dt><code class="code">{ <var class="var">statement_list</var> }</code></dt> <dd><p>This is the compound statement. It allows multiple statements to be grouped together for execution. </p> </dd> <dt><code class="code">if ( <var class="var">expression</var> ) <var class="var">statement1</var> [else <var class="var">statement2</var>]</code></dt> <dd><p>The if statement evaluates the expression and executes statement1 or statement2 depending on the value of the expression. If the expression is non-zero, statement1 is executed. If statement2 is present and the value of the expression is 0, then statement2 is executed. (The <code class="code">else</code> clause is an extension.) </p> </dd> <dt><code class="code">while ( <var class="var">expression</var> ) <var class="var">statement</var></code></dt> <dd><p>The while statement will execute the statement while the expression is non-zero. It evaluates the expression before each execution of the statement. Termination of the loop is caused by a zero expression value or the execution of a <code class="code">break</code> statement. </p> </dd> <dt><code class="code">for ( [<var class="var">expression1</var>] ; [<var class="var">expression2</var>] ; [<var class="var">expression3</var>] ) <var class="var">statement</var></code></dt> <dd><p>The <code class="code">for</code> statement controls repeated execution of the statement. <var class="var">Expression1</var> is evaluated before the loop. <var class="var">Expression2</var> is evaluated before each execution of the statement. If it is non-zero, the statement is evaluated. If it is zero, the loop is terminated. After each execution of the statement, <var class="var">expression3</var> is evaluated before the reevaluation of expression2. If <var class="var">expression1</var> or <var class="var">expression3</var> are missing, nothing is evaluated at the point they would be evaluated. If <var class="var">expression2</var> is missing, it is the same as substituting the value 1 for <var class="var">expression2</var>. (The optional expressions are an extension. POSIX <code class="command">bc</code> requires all three expressions.) The following is equivalent code for the <code class="code">for</code> statement: </p> <div class="example"> <pre class="example-preformatted">expression1; while (expression2) { statement; expression3; } </pre></div> </dd> <dt><code class="code">break</code></dt> <dd><p>This statement causes a forced exit of the most recent enclosing <code class="code">while</code> statement or <code class="code">for</code> statement. </p> </dd> <dt><code class="code">continue</code></dt> <dd><p>The <code class="code">continue</code> statement (an extension) causes the most recent enclosing <code class="code">for</code> statement to start the next iteration. </p> </dd> <dt><code class="code">halt</code></dt> <dd><p>The <code class="code">halt</code> statement (an extension) is an executed statement that causes the <code class="command">bc</code> processor to quit only when it is executed. For example, "if (0 == 1) halt" will not cause <code class="command">bc</code> to terminate because the <code class="code">halt</code> is not executed. </p> </dd> <dt><code class="code">return</code></dt> <dd><p>Return the value 0 from a function. (See <a class="xref" href="#Functions">Functions</a>.) </p> </dd> <dt><code class="code">return ( <var class="var">expression</var> )</code></dt> <dd><p>Return the value of the expression from a function. (See <a class="xref" href="#Functions">Functions</a>.) As an extension, the parenthesis are not required. </p></dd> </dl> <ul class="mini-toc"> <li><a href="#Pseudo-Statements" accesskey="1">Pseudo Statements</a></li> </ul> <hr> <div class="section-level-extent" id="Pseudo-Statements"> <div class="nav-panel"> <p> Previous: <a href="#Statements" accesskey="p" rel="prev">Statements</a>, Up: <a href="#Statements" accesskey="u" rel="up">Statements</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Pseudo-Statements-1"><span>4.1 Pseudo Statements<a class="copiable-link" href="#Pseudo-Statements-1"> ¶</a></span></h3> <p>These statements are not statements in the traditional sense. They are not executed statements. Their function is performed at "compile" time. </p> <dl class="table"> <dt><code class="code">limits</code></dt> <dd><p>Print the local limits enforced by the local version of <code class="command">bc</code>. This is an extension. </p> </dd> <dt><code class="code">quit</code></dt> <dd><p>When the <code class="code">quit</code> statement is read, the <code class="command">bc</code> processor is terminated, regardless of where the <code class="code">quit</code> statement is found. For example, "if (0 == 1) quit" will cause <code class="command">bc</code> to terminate. </p> </dd> <dt><code class="code">warranty</code></dt> <dd><p>Print a longer warranty notice. This is an extension. </p></dd> </dl> <hr> </div> </div> <div class="chapter-level-extent" id="Functions"> <div class="nav-panel"> <p> Next: <a href="#Examples" accesskey="n" rel="next">Examples</a>, Previous: <a href="#Statements" accesskey="p" rel="prev">Statements</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h2 class="chapter" id="Functions-1"><span>5 Functions<a class="copiable-link" href="#Functions-1"> ¶</a></span></h2> <p>Functions provide a method of defining a computation that can be executed later. Functions in <code class="command">bc</code> always compute a value and return it to the caller. Function definitions are "dynamic" in the sense that a function is undefined until a definition is encountered in the input. That definition is then used until another definition function for the same name is encountered. The new definition then replaces the older definition. A function is defined as follows: </p> <div class="example"> <pre class="example-preformatted"><code class="code">define</code> <var class="var">name</var> <code class="code">(</code> <var class="var">parameters</var> <code class="code">)</code> <code class="code">{</code> <var class="var">newline</var> <var class="var">auto_list statement_list</var> <code class="code">}</code> </pre></div> <p>A function call is just an expression of the form "<code class="code">name</code> <code class="code">(</code><var class="var">parameters</var><code class="code">)</code>". </p> <p>Parameters are numbers or arrays (an extension). In the function definition, zero or more parameters are defined by listing their names separated by commas. All parameters are call by value parameters. Arrays are specified in the parameter definition by the notation "<var class="var">name</var><code class="code">[ ]</code>". In the function call, actual parameters are full expressions for number parameters. The same notation is used for passing arrays as for defining array parameters. The named array is passed by value to the function. Since function definitions are dynamic, parameter numbers and types are checked when a function is called. Any mismatch in number or types of parameters will cause a runtime error. A runtime error will also occur for the call to an undefined function. </p> <p>The <var class="var">auto_list</var> is an optional list of variables that are for "local" use. The syntax of the auto list (if present) is "<code class="code">auto</code> <var class="var">name</var>, ... ;". (The semicolon is optional.) Each <var class="var">name</var> is the name of an auto variable. Arrays may be specified by using the same notation as used in parameters. These variables have their values pushed onto a stack at the start of the function. The variables are then initialized to zero and used throughout the execution of the function. At function exit, these variables are popped so that the original value (at the time of the function call) of these variables are restored. The parameters are really auto variables that are initialized to a value provided in the function call. Auto variables are different than traditional local variables because if function A calls function B, B may access function A’s auto variables by just using the same name, unless function B has called them auto variables. Due to the fact that auto variables and parameters are pushed onto a stack, <code class="command">bc</code> supports recursive functions. </p> <p>The function body is a list of <code class="command">bc</code> statements. Again, statements are separated by semicolons or newlines. Return statements cause the termination of a function and the return of a value. There are two versions of the return statement. The first form, "<code class="code">return</code>", returns the value 0 to the calling expression. The second form, "<code class="code">return</code> ( <var class="var">expression</var> )", computes the value of the expression and returns that value to the calling expression. There is an implied "<code class="code">return</code> (0)" at the end of every function. This allows a function to terminate and return 0 without an explicit <code class="code">return</code> statement. </p> <p>Functions also change the usage of the variable <var class="var">ibase</var>. All constants in the function body will be converted using the value of <var class="var">ibase</var> at the time of the function call. Changes of <var class="var">ibase</var> will be ignored during the execution of the function except for the standard function <code class="code">read</code>, which will always use the current value of <var class="var">ibase</var> for conversion of numbers. </p> <p>Several extensions have been added to functions. First, the format of the definition has been slightly relaxed. The standard requires the opening brace be on the same line as the <code class="code">define</code> keyword and all other parts must be on following lines. This version of <code class="command">bc</code> will allow any number of newlines before and after the opening brace of the function. For example, the following definitions are legal. </p> <div class="example"> <pre class="example-preformatted"> define d (n) { return (2*n); } define d (n) { return (2*n); } </pre></div> <p>Functions may be defined as <code class="code">void</code>. A void funtion returns no value and thus may not be used in any place that needs a value. A void function does not produce any output when called by itself on an input line. The key word <code class="code">void</code> is placed between the key word <code class="code">define</code> and the function name. For example, consider the following session. </p> <div class="example"> <pre class="example-preformatted">define py (y) { print "--->", y, "<---", "\n"; } define void px (x) { print "--->", x, "<---", "\n"; } py(1) --->1<--- 0 px(1) --->1<--- </pre></div> <p>Since <code class="code">py</code> is not a void function, the call of <code class="code">py(1)</code> prints the desired output and then prints a second line that is the value of the function. Since the value of a function that is not given an explicit return statement is zero, the zero is printed. For <code class="code">px(1)</code>, no zero is printed because the function is a void function. </p> <p>Also, call by variable for arrays was added. To declare a call by variable array, the declaration of the array parameter in the function definition looks like "<code class="code">*</code><var class="var">name</var><code class="code">[]</code>". The call to the function remains the same as call by value arrays. </p> <ul class="mini-toc"> <li><a href="#Math-Library-Functions" accesskey="1">Math Library Functions</a></li> </ul> <hr> <div class="section-level-extent" id="Math-Library-Functions"> <div class="nav-panel"> <p> Previous: <a href="#Functions" accesskey="p" rel="prev">Functions</a>, Up: <a href="#Functions" accesskey="u" rel="up">Functions</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h3 class="section" id="Math-Library-Functions-1"><span>5.1 Math Library Functions<a class="copiable-link" href="#Math-Library-Functions-1"> ¶</a></span></h3> <p>If <code class="command">bc</code> is invoked with the <code class="code">-l</code> option, a math library is preloaded and the default <var class="var">scale</var> is set to 20. The math functions will calculate their results to the scale set at the time of their call. The math library defines the following functions: </p> <dl class="table"> <dt><code class="code">s (<var class="var">x</var>)</code></dt> <dd><p>The sine of <var class="var">x</var>, <var class="var">x</var> is in radians. </p> </dd> <dt><code class="code">c (<var class="var">x</var>)</code></dt> <dd><p>The cosine of <var class="var">x</var>, <var class="var">x</var> is in radians. </p> </dd> <dt><code class="code">a (<var class="var">x</var>)</code></dt> <dd><p>The arctangent of <var class="var">x</var>, arctangent returns radians. </p> </dd> <dt><code class="code">l (<var class="var">x</var>)</code></dt> <dd><p>The natural logarithm of <var class="var">x</var>. </p> </dd> <dt><code class="code">e (<var class="var">x</var>)</code></dt> <dd><p>The exponential function of raising <var class="var">e</var> to the value <var class="var">x</var>. </p> </dd> <dt><code class="code">j (<var class="var">n</var>, <var class="var">x</var>)</code></dt> <dd><p>The Bessel function of integer order <var class="var">n</var> of <var class="var">x</var>. </p></dd> </dl> <hr> </div> </div> <div class="chapter-level-extent" id="Examples"> <div class="nav-panel"> <p> Next: <a href="#Readline-and-Libedit-Options" accesskey="n" rel="next">Readline and Libedit Options</a>, Previous: <a href="#Functions" accesskey="p" rel="prev">Functions</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h2 class="chapter" id="Examples-1"><span>6 Examples<a class="copiable-link" href="#Examples-1"> ¶</a></span></h2> <p>In /bin/sh, the following will assign the value of "pi" to the shell variable <var class="var">pi</var>. </p><div class="example"> <pre class="example-preformatted"> pi=$(echo "scale=10; 4*a(1)" | bc -l) </pre></div> <p>The following is the definition of the exponential function used in the math library. This function is written in POSIX <code class="command">bc</code>. </p> <div class="example"> <pre class="example-preformatted"> scale = 20 /* Uses the fact that e^x = (e^(x/2))^2 When x is small enough, we use the series: e^x = 1 + x + x^2/2! + x^3/3! + ... */ define e(x) { auto a, d, e, f, i, m, v, z /* Check the sign of x. */ if (x<0) { m = 1 x = -x } /* Precondition x. */ z = scale; scale = 4 + z + .44*x; while (x > 1) { f += 1; x /= 2; } /* Initialize the variables. */ v = 1+x a = x d = 1 for (i=2; 1; i++) { e = (a *= x) / (d *= i) if (e == 0) { if (f>0) while (f--) v = v*v; scale = z if (m) return (1/v); return (v/1); } v += e } } </pre></div> <p>The following is code that uses the extended features of <code class="command">bc</code> to implement a simple program for calculating checkbook balances. This program is best kept in a file so that it can be used many times without having to retype it at every use. </p> <div class="example"> <pre class="example-preformatted"> scale=2 print "\nCheck book program\n!" print " Remember, deposits are negative transactions.\n" print " Exit by a 0 transaction.\n\n" print "Initial balance? "; bal = read() bal /= 1 print "\n" while (1) { "current balance = "; bal "transaction? "; trans = read() if (trans == 0) break; bal -= trans bal /= 1 } quit </pre></div> <p>The following is the definition of the recursive factorial function. </p> <div class="example"> <pre class="example-preformatted"> define f (x) { if (x <= 1) return (1); return (f(x-1) * x); } </pre></div> <hr> </div> <div class="chapter-level-extent" id="Readline-and-Libedit-Options"> <div class="nav-panel"> <p> Next: <a href="#Comparison-with-Other-Implementations" accesskey="n" rel="next">Comparison with Other Implementations</a>, Previous: <a href="#Examples" accesskey="p" rel="prev">Examples</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h2 class="chapter" id="Readline-and-Libedit-Options-1"><span>7 Readline and Libedit Options<a class="copiable-link" href="#Readline-and-Libedit-Options-1"> ¶</a></span></h2> <p>GNU <code class="command">bc</code> can be compiled (via a configure option) to use the GNU <code class="command">readline</code> input editor library or the BSD <code class="command">libedit</code> library. This allows the user to do more editing of lines before sending them to <code class="command">bc</code>. It also allows for a history of previous lines typed. When this option is selected, <code class="command">bc</code> has one more special variable. This special variable, <var class="var">history</var> is the number of lines of history retained. A value of -1 means that an unlimited number of history lines are retained. This is the default value. Setting the value of <var class="var">history</var> to a positive number restricts the number of history lines to the number given. The value of 0 disables the history feature. For more information, read the user manuals for the GNU <code class="command">readline</code>, <code class="command">history</code> and BSD <code class="command">libedit</code> libraries. One can not enable both <code class="command">readline</code> and <code class="command">libedit</code> at the same time. </p> <hr> </div> <div class="chapter-level-extent" id="Comparison-with-Other-Implementations"> <div class="nav-panel"> <p> Next: <a href="#Limits" accesskey="n" rel="next">Limits</a>, Previous: <a href="#Readline-and-Libedit-Options" accesskey="p" rel="prev">Readline and Libedit Options</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h2 class="chapter" id="Comparison-with-Other-Implementations-1"><span>8 Comparison with Other Implementations<a class="copiable-link" href="#Comparison-with-Other-Implementations-1"> ¶</a></span></h2> <p>This version of <code class="command">bc</code> was implemented from the POSIX P1003.2/D11 draft and contains several differences and extensions relative to the draft and traditional implementations. It is not implemented in the traditional way using <code class="command">dc</code>. This version is a single process which parses and runs a byte code translation of the program. There is an "undocumented" option (-c) that causes the program to output the byte code to the standard output instead of running it. It was mainly used for debugging the parser and preparing the math library. </p> <p>A major source of differences is extensions, where a feature is extended to add more functionality and additions, where new features are added. The following is the list of differences and extensions. </p> <dl class="table"> <dt>LANG environment</dt> <dd><p>This version does not conform to the POSIX standard in the processing of the LANG environment variable and all environment variables starting with LC_. </p> </dd> <dt>names</dt> <dd><p>Traditional and POSIX <code class="command">bc</code> have single letter names for functions, variables and arrays. They have been extended to be multi-character names that start with a letter and may contain letters, numbers and the underscore character. </p> </dd> <dt>Strings</dt> <dd><p>Strings are not allowed to contain NUL characters. POSIX says all characters must be included in strings. </p> </dd> <dt>last</dt> <dd><p>POSIX <code class="command">bc</code> does not have a \fBlast variable. Some implementations of <code class="command">bc</code> use the period (.) in a similar way. </p> </dd> <dt>comparisons</dt> <dd><p>POSIX <code class="command">bc</code> allows comparisons only in the <code class="code">if</code> statement, the <code class="code">while</code> statement, and the second expression of the <code class="code">for</code> statement. Also, only one relational operation is allowed in each of those statements. </p> </dd> <dt><code class="code">if</code> statement, <code class="code">else</code> clause</dt> <dd><p>POSIX <code class="command">bc</code> does not have an <code class="code">else</code> clause. </p> </dd> <dt><code class="code">for</code> statement</dt> <dd><p>POSIX <code class="command">bc</code> requires all expressions to be present in the <code class="code">for</code> statement. </p> </dd> <dt><code class="code">&&,</code> <code class="code">||</code>, <code class="code">!</code></dt> <dd><p>POSIX <code class="command">bc</code> does not have the logical operators. </p> </dd> <dt><code class="code">read</code> function</dt> <dd><p>POSIX <code class="command">bc</code> does not have a <code class="code">read</code> function. </p> </dd> <dt><code class="code">print</code> statement</dt> <dd><p>POSIX <code class="command">bc</code> does not have a <code class="code">print</code> statement. </p> </dd> <dt><code class="code">continue</code> statement</dt> <dd><p>POSIX <code class="command">bc</code> does not have a continue statement. </p> </dd> <dt>array parameters</dt> <dd><p>POSIX <code class="command">bc</code> does not (currently) support array parameters in full. The POSIX grammar allows for arrays in function definitions, but does not provide a method to specify an array as an actual parameter. (This is most likely an oversight in the grammar.) Traditional implementations of <code class="command">bc</code> have only call by value array parameters. </p> </dd> <dt>function format</dt> <dd><p>POSIX <code class="command">bc</code> requires the opening brace on the same line as the <code class="code">define</code> key word and the <code class="code">auto</code> statement on the next line. </p> </dd> <dt><code class="code">=+</code>, <code class="code">=-</code>, <code class="code">=*</code>, <code class="code">=/</code>, <code class="code">=%</code>, <code class="code">=^</code></dt> <dd><p>POSIX <code class="command">bc</code> does not require these "old style" assignment operators to be defined. This version may allow these "old style" assignments. Use the <code class="code">limits</code> statement to see if the installed version supports them. If it does support the "old style" assignment operators, the statement "a =- 1" will decrement <code class="code">a</code> by 1 instead of setting <code class="code">a</code> to the value -1. </p> </dd> <dt>spaces in numbers</dt> <dd><p>Other implementations of <code class="command">bc</code> allow spaces in numbers. For example, "x=1 3" would assign the value 13 to the variable x. The same statement would cause a syntax error in this version of <code class="command">bc</code>. </p> </dd> <dt>errors and execution</dt> <dd><p>This implementation varies from other implementations in terms of what code will be executed when syntax and other errors are found in the program. If a syntax error is found in a function definition, error recovery tries to find the beginning of a statement and continue to parse the function. Once a syntax error is found in the function, the function will not be callable and becomes undefined. Syntax errors in the interactive execution code will invalidate the current execution block. The execution block is terminated by an end of line that appears after a complete sequence of statements. For example, </p> <div class="example"> <pre class="example-preformatted">a = 1 b = 2 </pre></div> <p>has two execution blocks and </p> <div class="example"> <pre class="example-preformatted">{ a = 1 b = 2 } </pre></div> <p>has one execution block. Any runtime error will terminate the execution of the current execution block. A runtime warning will not terminate the current execution block. </p> </dd> <dt>Interrupts</dt> <dd><p>During an interactive session, the SIGINT signal (usually generated by the control-C character from the terminal) will cause execution of the current execution block to be interrupted. It will display a "runtime" error indicating which function was interrupted. After all runtime structures have been cleaned up, a message will be printed to notify the user that <code class="command">bc</code> is ready for more input. All previously defined functions remain defined and the value of all non-auto variables are the value at the point of interruption. All auto variables and function parameters are removed during the clean up process. During a non-interactive session, the SIGINT signal will terminate the entire run of <code class="command">bc</code>. </p></dd> </dl> <hr> </div> <div class="chapter-level-extent" id="Limits"> <div class="nav-panel"> <p> Next: <a href="#Environment-Variables" accesskey="n" rel="next">Environment Variables</a>, Previous: <a href="#Comparison-with-Other-Implementations" accesskey="p" rel="prev">Comparison with Other Implementations</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h2 class="chapter" id="Limits-1"><span>9 Limits<a class="copiable-link" href="#Limits-1"> ¶</a></span></h2> <p>The following are the limits currently in place for this <code class="command">bc</code> processor. Some of them may have been changed by an installation. Use the <code class="code">limits</code> statement to see the actual values. </p> <dl class="table"> <dt><code class="code">BC_BASE_MAX</code></dt> <dd><p>The maximum output base is currently set at 999. The maximum input base is 16. </p> </dd> <dt><code class="code">BC_DIM_MAX</code></dt> <dd><p>This is currently an arbitrary limit of 65535 as distributed. Your installation may be different. </p> </dd> <dt><code class="code">BC_SCALE_MAX</code></dt> <dd><p>The number of digits after the decimal point is limited to INT_MAX digits. Also, the number of digits before the decimal point is limited to INT_MAX digits. </p> </dd> <dt><code class="code">BC_STRING_MAX</code></dt> <dd><p>The limit on the number of characters in a string is INT_MAX characters. </p> </dd> <dt><code class="code">exponent</code></dt> <dd><p>The value of the exponent in the raise operation (^) is limited to LONG_MAX. </p> </dd> <dt><code class="code">multiply</code></dt> <dd><p>The multiply routine may yield incorrect results if a number has more than LONG_MAX / 90 total digits. For 32 bit longs, this number is 23,860,929 digits. </p> </dd> <dt><code class="code">variable names</code></dt> <dd><p>The current limit on the number of unique names is 32767 for each of simple variables, arrays and functions. </p></dd> </dl> <hr> </div> <div class="chapter-level-extent" id="Environment-Variables"> <div class="nav-panel"> <p> Previous: <a href="#Limits" accesskey="p" rel="prev">Limits</a>, Up: <a href="#Top" accesskey="u" rel="up">Top</a> [<a href="#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p> </div> <h2 class="chapter" id="Environment-Variables-1"><span>10 Environment Variables<a class="copiable-link" href="#Environment-Variables-1"> ¶</a></span></h2> <p>The following environment variables are processed by <code class="command">bc</code>: </p> <dl class="table"> <dt><code class="code">POSIXLY_CORRECT</code></dt> <dd><p>This is the same as the -s option (see <a class="pxref" href="#Command-Line-Options">Command Line Options</a>). </p> </dd> <dt><code class="code">BC_ENV_ARGS</code></dt> <dd><p>This is another mechanism to get arguments to <code class="command">bc</code>. The format is the same as the command line arguments. These arguments are processed first, so any files listed in the environment arguments are processed before any command line argument files. This allows the user to set up "standard" options and files to be processed at every invocation of <code class="command">bc</code>. The files in the environment variables would typically contain function definitions for functions the user wants defined every time <code class="command">bc</code> is run. </p> </dd> <dt><code class="code">BC_LINE_LENGTH</code></dt> <dd><p>This should be an integer specifying the number of characters in an output line for numbers. This includes the backslash and newline characters for long numbers. As an extension, the value of zero disables the multi-line feature. Any other value of this variable that is less than 3 sets the line length to 70. </p></dd> </dl> </div> </body> </html>
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