Expr - Revision history

Christoph: Expr (command) moved to Expr

2007-04-26T01:59:04Z

Expr (command) moved to Expr

Christoph at 01:58, 26 April 2007

2007-04-26T01:58:21Z

Christoph at 02:15, 19 October 2006

2006-10-19T02:15:24Z

Christoph at 01:44, 19 October 2006

2006-10-19T01:44:25Z

New page

{{lowercase|expr}}
'''expr''' is a [[:Category:Linux Command Line Tools|command line]] utility which evaluates an expression and outputs the corresponding value.

''expr'' evaluates integer or string expressions, including pattern matching [[regular expression]]s. Most of the challenge posed in writing expressions is preventing the command line shell from acting on characters intended for ''expr'' to process.

The operators available:
* for integers: addition, subtraction, multiplication, division and modulus
* for strings: find substring, find regular expression, find a set of characters in a string, length of string
* for either: comparison (equal, not equal, less than, etc.)
Also, boolean expressions involving ''and'' and ''or'', such as
expr length "abcdef" \< 5 "|" 15 - 4 ">" 8
outputs "1". This is because length "abcdef" is 6, which is not less than (the backslash escapes a less than from the shell) 5 (so the left side of the | returns zero). But 15 minus 4 is 11 and is greater than 8, so the right side is true, which makes the ''or'' true, so 1 is the result. (The return value—the program exit status—is zero for this example.)

== man page ==
Usage: expr EXPRESSION
or: expr OPTION

Print the value of EXPRESSION to standard output. A blank line below separates increasing precedence groups. EXPRESSION may be:
<pre>
ARG1 | ARG2 ARG1 if it is neither null nor 0, otherwise ARG2
ARG1 & ARG2 ARG1 if neither argument is null or 0, otherwise 0
ARG1 < ARG2 ARG1 is less than ARG2
ARG1 <= ARG2 ARG1 is less than or equal to ARG2
ARG1 = ARG2 ARG1 is equal to ARG2
ARG1 != ARG2 ARG1 is unequal to ARG2
ARG1 >= ARG2 ARG1 is greater than or equal to ARG2
ARG1 > ARG2 ARG1 is greater than ARG2
ARG1 + ARG2 arithmetic sum of ARG1 and ARG2
ARG1 - ARG2 arithmetic difference of ARG1 and ARG2
ARG1 * ARG2 arithmetic product of ARG1 and ARG2
ARG1 / ARG2 arithmetic quotient of ARG1 divided by ARG2
ARG1 % ARG2 arithmetic remainder of ARG1 divided by ARG2

STRING : REGEXP anchored pattern match of REGEXP in STRING

match STRING REGEXP same as STRING : REGEXP
substr STRING POS LENGTH substring of STRING, POS counted from 1
index STRING CHARS index in STRING where any CHARS is found, or 0
length STRING length of STRING
+ TOKEN interpret TOKEN as a string, even if it is a
keyword like `match' or an operator like `/'

( EXPRESSION ) value of EXPRESSION
</pre>

Beware that many operators need to be escaped or quoted for shells. Comparisons are arithmetic if both ARGs are numbers, else lexicographical. Pattern matches return the string matched between \( and \) or null; if \( and \) are not used, they return the number of characters matched or 0.

==External links==
* [http://www.linuxmanpages.com/man1/expr.1.php The <code>expr</code> manpage]

{{stub}}
[[Category:Linux Command Line Tools]]

@@ Line 1: / Line 1: @@
 '''expr''' is a [[:Category:Linux Command Line Tools|command line]] utility which evaluates an expression and outputs the corresponding value.
@@ Line 46: / Line 45: @@
 Beware that many operators need to be escaped or quoted for shells. Comparisons are arithmetic if both ARGs are numbers, else lexicographical. Pattern matches return the string matched between \( and \) or null; if \( and \) are not used, they return the number of characters matched or 0.
-== See also ==
+==See also==
-* [[Coreutils]]
+*[[Coreutils]]
 ==External links==
-* [http://www.linuxmanpages.com/man1/expr.1.php The <code>expr</code> manpage]
+*[http://www.linuxmanpages.com/man1/expr.1.php The <code>expr</code> manpage]
 [[Category:Linux Command Line Tools]]

← Older revision		Revision as of 02:15, 19 October 2006
Line 45:		Line 45:

	Beware that many operators need to be escaped or quoted for shells. Comparisons are arithmetic if both ARGs are numbers, else lexicographical. Pattern matches return the string matched between \( and \) or null; if \( and \) are not used, they return the number of characters matched or 0.		Beware that many operators need to be escaped or quoted for shells. Comparisons are arithmetic if both ARGs are numbers, else lexicographical. Pattern matches return the string matched between \( and \) or null; if \( and \) are not used, they return the number of characters matched or 0.
		+
		+	== See also ==
		+	* [[Coreutils]]

	==External links==		==External links==

← Older revision	Revision as of 01:59, 26 April 2007
(No difference)