Extract substring using regexp in plain bash

I'm trying to extract the time from a string using bash, and I'm having a hard time figuring it out.

My string is like this:

US/Central - 10:26 PM (CST) 

And I want to extract the 10:26 part.

Anybody knows of a way of doing this only with bash - without using sed, awk, etc?

Like, in PHP I would use - not the best way, but it works - something like:

preg_match( ""(\d{2}\:\d{2}) PM \(CST\)"", "US/Central - 10:26 PM (CST)", $matches ); 

Thanks for any help, even if the answer uses sed or awk

6 Answers

Using pure bash :

$ cat file.txt US/Central - 10:26 PM (CST) $ while read a b time x; do [[ $b == - ]] && echo $time; done < file.txt 

another solution with bash regex :

$ [[ "US/Central - 10:26 PM (CST)" =~ -[[:space:]]*([0-9]{2}:[0-9]{2}) ]] && echo ${BASH_REMATCH[1]} 

another solution using grep and look-around advanced regex :

$ echo "US/Central - 10:26 PM (CST)" | grep -oP "\-\s+\K\d{2}:\d{2}" 

another solution using sed :

$ echo "US/Central - 10:26 PM (CST)" | sed 's/.*\- *\([0-9]\{2\}:[0-9]\{2\}\).*/\1/' 

another solution using perl :

$ echo "US/Central - 10:26 PM (CST)" | perl -lne 'print $& if /\-\s+\K\d{2}:\d{2}/' 

and last one using awk :

$ echo "US/Central - 10:26 PM (CST)" | awk '{for (i=0; i<=NF; i++){if ($i == "-"){print $(i+1);exit}}}' 

 echo "US/Central - 10:26 PM (CST)" | sed -n "s/^.*-\s*\(\S*\).*$/\1/p" -n suppress printing s substitute ^.* anything at the beginning - up until the dash \s* any space characters (any whitespace character) \( start capture group \S* any non-space characters \) end capture group .*$ anything at the end \1 substitute 1st capture group for everything on line p print it 

Quick 'n dirty, regex-free, low-robustness chop-chop technique

string="US/Central - 10:26 PM (CST)" etime="${string% [AP]M*}" etime="${etime#* - }" 

If your string is

foo="US/Central - 10:26 PM (CST)" 

then

echo "${foo}" | cut -d ' ' -f3 

will do the job.

No need to open a pipe and spawn sed or awk to extract the 10:26 (time) part. Bash can easily handle this.

input="US/Central - 10:26 PM (CST)" [[ $input =~ ([0-9]+:[0-9]+) ]] echo ${BASH_REMATCH[1]} 

Outputs:

10:26 

If you're using zsh, it's the same, except the match result will be in $match[1] instead of $BASH_REMATCH[1]

In 2023, I don't think the extra pipe to grep, sed, awk or perl are relevant, especially when the question is:

Anybody knows of a way of doing this only with bash - without using sed, awk, etc?

foo="US/Central - 10:26 PM (CST)"

echo ${foo} | date +%H:%M