read from second character till first occurrence of separator-CodePudding

This is how my variable name looks like: p123456_19100210720_linux-86-64

I am trying to get 123456 in a variable using variable expansion. I am able to get p123456 using variable expansion and reading everything before first _.

patchname="p123456_19100210720_linux-86-64"
echo ${patchname%%*_}

This outputs p123456. Is there a way I can get only 123456?

CodePudding user response：

It will be much easier using BASH regex operator:

[[ $patchname =~ [0-9]  ]] && echo "${BASH_REMATCH[0]}"

123456

Alternative solution using extglob:

shopt -s extglob
echo "${patchname// ([^0-9]|_*)/}"

123456

CodePudding user response：

You can remove the letters prior to removing everything after _ if using bash is the preferred option

$ patchname=$(echo "${patchname//[a-z]}")
$ echo "${patchname//_*/}"
123456

Using sed will be easier

$ sed 's/[a-z]\(.[^_]*\).*/\1/' <<< "$patchname"
123456