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Top Forums Shell Programming and Scripting Increment a variable in unix bash Post 302629145 by Corona688 on Tuesday 24th of April 2012 11:12:31 AM
Old 04-24-2012
If you're really in BASH:

Code:
((S++))

will suffice.

If you want to use expr, remember that each thing you feed expr must be a separate argument. That means putting in spaces.

Code:
S=`expr $S + 1`

 

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let(1)								   User Commands							    let(1)

NAME
let - shell built-in function to evaluate one or more arithmetic expressions SYNOPSIS
ksh let arg... ksh93 let [expr...] DESCRIPTION
ksh Each arg is a separate arithmetic expression to be evaluated. ksh93 let evaluates each expr in the current shell environment as an arithmetic expression using ANSI C syntax. Variables names are shell vari- ables and they are recursively evaluated as arithmetic expressions to get numerical values. let has been made obsolete by the ((...)) syn- tax of ksh93(1) which does not require quoting of the operators to pass them as command arguments. EXIT STATUS
ksh ksh returns the following exit values: 0 The value of the last expression is non-zero. 1 The value of the last expression is zero. ksh93 ksh93 returns the following exit values: 0 The last expr evaluates to a non-zero value. >0 The last expr evaluates to 0 or an error occurred. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ SEE ALSO
ksh(1), ksh93(1), set(1), typeset(1), attributes(5) SunOS 5.11 2 Nov 2007 let(1)
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