A number of articles in the web give examples of how to use the bash regular expression operator =~ that exists since bash version 3. However the majority of these examples did not work for me.
The enlightenment occured when I had fully digested the sentence Any part of the pattern may be quoted to force it to be matched as a string. That means this example (taken from http://aplawrence.com/Linux/bash-regex.html) does not work:
if [[ "$input" =~ 'foo(.*)' ]]
then
echo $BASH_REMATCH is what I wanted
echo but just ${BASH_REMATCH[1]}
fi
The reason is that the regular expression is quoted with single quotes and thus matched as a string. A regular expression like ...
([0-9]+) ([0-9]+) ([0-9]+) ([0-9]+) ([a-z/0-9]+)
... will actually trigger an error, since the shell will try to interpret the breakets as shell grammar. One solution I found to this mess is to assign the regular expression to a variable and then match against this variable:
regex='([0-9]+) ([0-9]+) ([0-9]+) ([0-9]+) ([a-z/0-9]+)'
if [[ "${params}" =~ $regex ]]
then
case "${BASH_REMATCH[5]}" in
There's probably a simpler way, but this one at least works. ;)
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