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Diffstat (limited to 'docs/busybox.sgml')
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diff --git a/docs/busybox.sgml b/docs/busybox.sgml index ec6f504..a25aa01 100644 --- a/docs/busybox.sgml +++ b/docs/busybox.sgml @@ -879,6 +879,58 @@ </para> </sect1> + <sect1 id="expr"> + <title>expr</title> + + <para> + Usage: expr EXPRESSION + </para> + + <para> + Prints the value of EXPRESSION to standard output. + </para> + + <para> + EXPRESSION may be: + </para> + + <para> + <screen> + 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 + quote TOKEN interpret TOKEN as a string, even if it is a + keyword like `match' or an operator like `/' + ( EXPRESSION ) value of EXPRESSION + </screen> + </para> + + <para> + 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. + </para> + + </sect1> + + <sect1 id="false"> <title>false</title> |