Question

I write the following shell script.

#! /bin/sh

foo=asdfqwer/asdfxv

if [ $foo = */* ]
then
    echo bad
else
    echo good
fi

in test command, we could compare string and pattern like this,

[ string = pattern ]

[ string == pattern ]

however, the above script always print “good” in the terminal and also has error as below:

[ : asdfqwer/asdfxv : unexpected operator

Can someone tells me why and how to compare a stirng and a pattern in shell scripting?

Answer 1

The test command (or [ command), does not do globbed comparison. Instead, the shell is expanding the */* to match files in your directory, and substituting them in to that command. Presumably, one of the filenames gets parsed as an operator to the [ command, and is invalid.

The best way to compare against globs is case:

#!/bin/sh

foo=asdfqwer/asdfxv

case "$foo" in
   */*) echo bad ;;
   *) echo good ;;
esac