从man中摘下expr用法

时间：2006-11-23 来源：softwindow

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

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