Assign sed command correctly

Question

I am trying to assign the result of a sed command to a variable in bash, but I am unable to escape everything corrrectly (probably just due to my lack of knowledge in bash), I have tried:

hash_in_podfile=$( sed -rn 's/^ *pod [\'\"]XXX["\'],.*:commit *=> *["\']([^\'"]*)["\'].*$/\1/p' ${PODS_PODFILE_DIR_PATH}/Podfile )

but I am getting

bash_playground.sh: line 9: unexpected EOF while looking for matching `''

UPDATED SCRIPT

This is the script I am using updated with the code from the answer. Only the path and the comment have changed:

#!\bin\sh
PODS_PODFILE_DIR_PATH='/Users/path/to/file'

# just a comment
hash_in_podfile=$(sed -rnf - <<\! -- "${PODS_PODFILE_DIR_PATH}/Podfile"
s/^ *pod ['"]XXX["'],.*:commit *=> *["']([^'"]*)["'].*$/\1/p
!
)
echo $hash_in_podfile

executed with sh script_name.sh

sh --version yields:

GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin20) Copyright (C) 2007 Free Software Foundation, Inc.

On execution I get:

script_name.sh: line 6: unexpected EOF while looking for matching `"'
script_name.sh: line 10: syntax error: unexpected end of file

Answer 1

There are two issues in your script:

1. The sh on macOS is a very old version of the bash shell, and it has a bug that stops you from using unbalanced quotes in here-documents in command substitutions:

   $ a=$( cat <<'END'
   > "
   > END
   > )
   > sh: unexpected EOF while looking for matching `"'
   

   (I had to press Ctrl+D after the ) at the end there.)

   You can get by this by installing a newer bash shell from the Homebrew package manager (or equivalent), or by using the zsh shell on macOS.

2. The sed on macOS does not have an -r option. To use extended regular expressions with sed on macOS, use -E (this is also supported by GNU sed nowadays). Your expression does not use extended regular expression features though, so just removing the option would be ok too. macOS sed also can't use - as the option-argument to -f to mean "read from standard input". Use /dev/stdin instead.

Suggestion:

#!/bin/zsh

PODS_PODFILE_DIR_PATH='/Users/path/to/file'

# just a comment

hash_in_podfile=$(sed -n -f /dev/stdin -- $PODS_PODFILE_DIR_PATH/Podfile <<'END'
s/^ *pod ['"]XXX["'],.*:commit *=> *["']([^'"]*)["'].*$/\1/p
END
)

echo $hash_in_podfile

If all you want to do is to output the value, then don't use an intermediate variable:

#!/bin/zsh

PODS_PODFILE_DIR_PATH='/Users/path/to/file'

# just a comment

sed -n -f /dev/stdin -- $PODS_PODFILE_DIR_PATH/Podfile <<'END'
s/^ *pod ['"]XXX["'],.*:commit *=> *["']([^'"]*)["'].*$/\1/p
END

Answer 2

If the heredoc approach doesn't work for your system, then you can go fir an alternative of providing sed commands via shell variables:

hash_in_podfile=$(q=\"\'; sed -ne "s/^ *pod [$q]XXX[$q],.*:commit *=> *[$q]([^$q]*)[$q].*\$/\\1/p" -- "${PODS_PODFILE_DIR_PATH}/Podfile")

Although there are many ways you could do this, but the simplest is to supply the sed commands on the stdin via a quoted heredoc so that there is no need to escape sed characters which are meaningful for the shell.

hash_in_podfile=$(sed -rnf - <<\! -- "${PODS_PODFILE_DIR_PATH}/Podfile"
s/^ *pod ['"]XXX["'],.*:commit *=> *["']([^'"]*)["'].*$/\1/p
!
)

Answer 3

hash_in_podfile="$( sed -rn 's/^ *pod ['\''"]XXX["'\''],.*:commit *=> *["'\'']([^'\''"]*)["'\''].*$/\1/p' "${PODS_PODFILE_DIR_PATH}/Podfile" )"

The basic “trick” is in the way single-quotes are “escaped” within single-quotes: echo 'before'\''after' yields before'after. Given the way Bash expansion works, this will form a single token, as expected. An equivalent option would be echo 'before'"'"'after', but the former syntax is slightly shorter.

To check whether the expanded command looks right, just print it out:

echo sed -rn 's/^ *pod ['\''"]XXX["'\''],.*:commit *=> *["'\'']([^'\''"]*)["'\''].*$/\1/p' "${PODS_PODFILE_DIR_PATH}/Podfile"

BTW, it is good practice to use up-to-date software (e.g. version 5.1.8 in case of Bash) instead of badly outdated versions. In some cases a huge version discrepancy can make problems hard to reproduce and advice hard to follow.