Passing string as input raises "sed: unsupported command e" on Alpine

[adnan360]

I tried something like this on a GitLab build based on Alpine Linux:

BODY_SOURCE=$(echo "$BODY_SOURCE" | sh inc/markdown.bash/markdown.sh /dev/stdin)

It works on a Void Linux machine just fine, but not on Alpine. It gave me a:

sed: unsupported command e

It seems to be doing this on this line of markdown.sh:

while grep '^[\*\+\-] ' "$temp_file" >/dev/null

[escoand]

Had the same problem. The solution is to install a full sed with apk add sed.

[jadutter]

That error sed: unsupported command e happens when you try to use non-GNU sed.
GNU sed supports a substitution flag e that is not supported by BSD sed. The flag tells sed to execute the line in sh to get what the replacement should be, s/find_me/echo hello world/e;

The README.md mentions that it needs GNU sed.

Here's a short demo of using the e flag in GNU sed

SED="$(which gsed sed 2>/dev/null | head -n 1)"
if [[ "${#SED}" -eq 0 ]]; then
    echo "Failed to find sed! Double check you PATH variable."
elif ! {
        printf '%s\n' world "$(whoami)" |\
            "${SED}" -E 's,^(.+)$,printf "hello %16s!\n" "\1",e;' && \
            printf '\n'
    }; then
    echo "You do not appear to have GNU sed."
else
    printf '%s\n' sed gsed sh bash zsh fish dash ash |\
    ${SED} -E '
        # insert headers before the first line
        1{
            i\
NAME     REALPATH
        }

        # for each line print the basename and realpath
        s,^(.+)$,printf "%-8s %s\\n" "$(basename \1)" "$(realpath "$(which \1 2>/dev/null)" 2>/dev/null)" ,ge;
    '
fi

# hello            world!
# hello             user!

# NAME     REALPATH
# sed      /usr/bin/sed
# gsed     /opt/homebrew/Cellar/gnu-sed/3.2/bin/gsed
# sh       /bin/sh
# bash     /bin/bash
# zsh      
# fish
# dash     
# ash

For macOS users, brew install coreutils will retrieve the GNU version of common utils (such as sed), adding gsed (GNU sed) as a command.