problem in string comparison in shell programming

salman4u · #1 (**permalink**) 02-25-2009

Hello,
was just wondering how to compare strings in unix? I mean as in C there is a function strcmp() in string.h, is there any function in unix for that? I tried using

Code:

    if [ "p" > "q" ]

and all such variations but didn't succeed. Any help would be appreciated. Thanks in advance

Shahul · #2 (**permalink**) 02-25-2009

Hi,

you can compare string..like below..

if [ $valuea -ge $valueb ]
then
command
else
command
fi

to compare two strings..

you can use lessthan --> -le
greater than -ge
equal -eq

Thanks
Sha

avi.skynet · #3 (**permalink**) 02-25-2009

hi
you can compare the string by the following commands as u have told strcmp() in C
if [ "$string1" == "$string2" ]
then

else

fi

salman4u · #4 (**permalink**) 02-26-2009

Quote:

Originally Posted by Shahul

Hi,

you can compare string..like below..

if [ $valuea -ge $valueb ]
then
command
else
command
fi

to compare two strings..

you can use lessthan --> -le
greater than -ge
equal -eq

Thanks
Sha

I dont think you can compare strings with -le -gt -ge. It's meant for only integer comparison.

cfajohnson · #5 (**permalink**) 02-25-2009

Quote:

Originally Posted by salman4u

was just wondering how to compare strings in unix? I mean as in C there is a function strcmp() in string.h, is there any function in unix for that? I tried using

Code:

    if [ "p" > "q" ]

and all such variations but didn't succeed. Any help would be appreciated. Thanks in advance

In bash, you can compare alphabetically, but it is not standard. You need to escape the angle bracket:
Code:
if [ p \> q ]

salman4u · #6 (**permalink**) 02-26-2009

Quote:

Originally Posted by cfajohnson

In bash, you can compare alphabetically, but it is not standard. You need to escape the angle bracket:
Code:
if [ p \> q ]

cfajohnson

You're the man. Thanks!!

fpmurphy · #7 (**permalink**) 02-26-2009

Just a quick note - the string comparison is based on the ASCII value of the characters in the string and may fail for strings containing non-ASCII characters.

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