trying to replace a string in sed with embedded { and $ and with -E or -r, the { is problematic for me.
according to the docs and many examples I have read, I should only have to escape the { and $ if testing for them. I have whittled it down the simplest case (below)
Probably something I do not understand
I can use my workaround, but this is something that should work with the \{ ?
Given string:
: "${TARGET_PART:=${MMC_PART2}}"
and part=5
I want to replace the ${MMC_PART2}} with ${MMC_PART5}}
The following does not work:
echo ': "${TARGET_PART:=${MMC_PART2}}"'| sed -r "s/:=\{(MMC_PART).}}/\1$part}}/g"
but the following does work - (replaced "{" with ".")
echo ': "${TARGET_PART:=${MMC_PART2}}"'| sed -r "s/:=.(MMC_PART).}}/\1$part}}/g"
What am I missing?
Your sed command is syntactically correct but fails to account for the $ in:
: "${TARGET_PART:=${MMC_PART2}}"
The replacement seems wrong too.
The first command should be:
part=5
echo ': "${TARGET_PART:=${MMC_PART2}}"'| sed -r "s/(:=\\\$\{MMC_PART).(}})/\1$part\2/g"
to output:
: "${TARGET_PART:=${MMC_PART5}}"
Note that inside double-quotes, backslash and dollar should be escaped to avoid alteration by the shell. Inside single-quotes, this is not necessary:
echo ': "${TARGET_PART:=${MMC_PART2}}"'| sed -r 's/(:=\$\{MMC_PART).(}})/\1'"$part"'\2/g'
Your second command does not perform any substitution for me. Perhaps it was transcribed incorrectly into the question.