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Shell Programming and Scripting

Substraction in shell scripting

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# 1  
Old 12-10-2012
Substraction in shell scripting
Hello friends,

I am new on linux, i am facing issues on below script.

Code:
#!/bin/sh
current=1355147377
echo $current
last_modified=1354537347
echo $last_modified
DIFF='expr ($current - $last_modified)' 
echo $DIFF

Moderator's Comments:
Mod Comment Please view this code tag video for how to use code tags when posting code and data.
Last edited by radoulov; 12-10-2012 at 10:07 AM..
# 2  
Old 12-10-2012
Quote:
Originally Posted by sanjay833i
#!/bin/sh
current=1355147377
echo $current
last_modified=1354537347
echo $last_modified
DIFF='expr ($current - $last_modified)'
echo $DIFF
try this

Code:
DIFF=`expr $current - $last_modified`

or
Code:
DIFF=$(expr $current - $last_modified)

# 3  
Old 12-10-2012
Hi try this one

Use the symbol on that is on "~" on your key board
Code:
DIFF=`expr $current - $last_modified`

# 4  
Old 12-11-2012
its now working,error i am getting

expr: non-numeric argument
: command not found:

i am more describing my work file
Code:
#!/bin/sh
current=$(date +"%s")
echo $current
last_modified=$(stat -c %Y franchise_form.html)
echo $last_modified
DIFF=$(expr $current - $last_modified) 
echo $DIFF

---------- Post updated 12-11-12 at 05:07 PM ---------- Previous update was 12-10-12 at 09:15 PM ----------

its resolved !
Code:
current=$(date +"%s")
last_modified=$(stat -c %Y ../offerDetails.php)
DIFF=$(($(($current-$last_modified))))
echo $DIFF

# 5  
Old 12-11-2012
Try:
Code:
DIFF=$((current-last_modified))

# 6  
Old 12-11-2012
As a note, $(( )) does not work in some /bin/sh. You should specify /bin/bash or /bin/ksh when using features that require /bin/bash or /bin/ksh
# 7  
Old 12-11-2012
$(( .. )) is part of the POSIX specification, so in practice it should work with /bin/sh on almost any modern Unix / Linux (On Solaris <=10 use /usr/xpg4/bin/sh)
This User Gave Thanks to Scrutinizer For This Post:
sanjay833i
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