bash search for a pattern within a string variable

nutthick · 05-24-2006, 06:17 AM

Does anyone know a bash command to check for a pattern match within a string. For example, if I have a string "1 2 3 4 5". I need a function that would return true if I searched for "2 3", but false if I searched for "8 9".

Thanks

PS I tried searching this forum, but the search kept locking up, so sorry if this has been answered already.

druuna · 05-24-2006, 10:14 AM

Hi,

I don't know any bash internal that can do this, but the following code snippet is one way of solving this (there are probably a lot more):

Code:

#!/bin/bash

thisString="1 2 3 4 5"

searchString="8 9"

if `echo ${thisString} | grep "${searchString}" 1>/dev/null 2>&1`
then
  echo "True"
else
  echo "False"
fi

Hope this helps.

spirit receiver · 05-24-2006, 12:51 PM

There are built-in tests for extended regular expressions (similar to what druuna uses) or Bash patterns:

Code:

#! /bin/bash

VARIABLE="Let's test this string!"

# This is for regular expressions:
if [[ "$VARIABLE" =~ "Let's.*ring" ]]
then
    echo "matched"
else
    echo "nope"
fi

# And here we have Bash Patterns:
if [[ "$VARIABLE" == L*ing! ]]
then
    echo "matched"
else
    echo "nope"
fi

nutthick · 05-31-2006, 01:27 AM

Thanks I've got it working now

Columbo2 · 07-06-2008, 10:32 PM

It works more like this:

Code:

kovacsbv@leviticus:~$ cat tmp.sh
#! /bin/bash

VARIABLE="Let's test this string!"

# This is for regular expressions:
if [[ "$VARIABLE" =~ "Let's.*ring" ]]
then
    echo "#1 matched"
else
    echo "#1 nope"
fi

if [[ "$VARIABLE" =~ Let\'s.*ring ]]
then
    echo "#2 matched"
else
    echo "#2 nope"
fi
kovacsbv@leviticus:~$ ./tmp.sh
#1 nope
#2 matched
kovacsbv@leviticus:~$

simon.sweetman · 02-16-2011, 05:16 PM

To get #1 matching remove quotes around RE or set compat31

Code:

shopt -s compat31

gnashley · 02-17-2011, 03:53 AM

Actually 'case' is much much faster than even simple matching using 'if', and
can even do pattern and glob matching:

Code:

#!/bin/sh

thisString="1 2 3 4 5"
searchString="1 2"
# if you single quote your input, you could do this
# searchString=$1

case $thisString in
  # match exact string
  "$searchString") echo yep, it matches exactly;;
  
  # match start of string
  "$searchString"*) echo yep, it matches at the start ;;

  # match end of string
  *"$searchString") echo yep, it matches at the end ;;

  # searchString can be anywhere in thisString
  *"$searchString"*) echo yep, it matches in the middle somewhere ;;
  
  *) echo nope ;;
esac

lastsurvivor · 03-06-2012, 03:54 AM

Thanks brother !

Quote:

Originally Posted by gnashley

Actually 'case' is much much faster than even simple matching using 'if', and
can even do pattern and glob matching:

Code:

#!/bin/sh

thisString="1 2 3 4 5"
searchString="1 2"
# if you single quote your input, you could do this
# searchString=$1

case $thisString in
  # match exact string
  "$searchString") echo yep, it matches exactly;;
  
  # match start of string
  "$searchString"*) echo yep, it matches at the start ;;

  # match end of string
  *"$searchString") echo yep, it matches at the end ;;

  # searchString can be anywhere in thisString
  *"$searchString"*) echo yep, it matches in the middle somewhere ;;
  
  *) echo nope ;;
esac