How do you tell if a string contains another string in Unix shell scripting?
I want to write a Unix shell script that will do various logic if there is a string inside of another string. For example, if I am in a certain folder, branch off. Could someone please tell me how to accomplish this? If possible I would like to make this not shell specific (ie not bash only) but if there's no other way I can make do with that.
#!/usr/bin/env sh
if [ "$PWD" contains "String1" ]
then
echo "String1 present"
elif [ "$PWD" contains "String2" ]
then
echo "String2 present"
else
echo "Else"
fi
Here's yet another solution. This uses POSIX substring parameter expansion, so it works in bash, dash, ksh...
test "${string#*$word}" != "$string" && echo "$word found in $string"
Edit: That's a great idea, C. Ross. Here's a functionalized version with some examples:
# contains(string, substring)
#
# Returns 0 if the specified string contains the specified substring,
# otherwise returns 1.
contains() {
string="$1"
substring="$2"
if test "${string#*$substring}" != "$string"
then
return 0 # $substring is in $string
else
return 1 # $substring is not in $string
fi
}
contains "abcd" "e" || echo "abcd does not contain e"
contains "abcd" "ab" && echo "abcd contains ab"
contains "abcd" "bc" && echo "abcd contains bc"
contains "abcd" "cd" && echo "abcd contains cd"
contains "abcd" "abcd" && echo "abcd contains abcd"
contains "" "" && echo "empty string contains empty string"
contains "a" "" && echo "a contains empty string"
contains "" "a" || echo "empty string does not contain a"
contains "abcd efgh" "cd ef" && echo "abcd efgh contains cd ef"
contains "abcd efgh" " " && echo "abcd efgh contains a space"
Pure POSIX shell:
#!/bin/sh
CURRENT_DIR=`pwd`
case "$CURRENT_DIR" in
*String1*) echo "String1 present" ;;
*String2*) echo "String2 present" ;;
*) echo "else" ;;
esac
Extended shells like ksh or bash have fancy matching mechanisms, but the old-style case is surprisingly powerful.
Sadly, I am not aware of a way to do this in sh. However, using bash (starting in version 3.0.0, which is probably what you have), you can use the =~ operator like this:
#!/bin/bash
CURRENT_DIR=`pwd`
if [[ "$CURRENT_DIR" =~ "String1" ]]
then
echo "String1 present"
elif [[ "$CURRENT_DIR" =~ "String2" ]]
then
echo "String2 present"
else
echo "Else"
fi
As an added bonus (and/or a warning, if your strings have any funny characters in them), =~ accepts regexes as the right operand if you leave out the quotes.
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