Re: No escape from the dollar sign in SED

Hi,


You could do the following also:


cat <<-'EOF' | sed -e "s|[$]path|$usb|g"
echo and here it is:
ftpdir=$path
echo more stuff
EOF

But you have to also ensure that "$usb" shell variable contents DONOT have anything which might be considered special by "sed" on it's right-hand-side of it's
"s///" command, because otherwise this will cause sed to error out.

For that you could do the following:

usb_rhs=$(printf '%s\n' "$usb" | sed -e 's:[|\&]:\\&:g;$!s/$/\\/');

Now use this variable ($usb_rhs) in your "sed" command. It properly escapes the characters that are metacharacters to sed on the rhs of s/// command.

________________________________
From: [email protected] <[email protected]> on behalf of [email protected] [sed-users] <[email protected]>
Sent: Tuesday, April 3, 2018 9:07 PM
To: [email protected]
Subject: No escape from the dollar sign in SED



I was reading the excellent SED FAQ bud could not find an alternate solution to the following:

The script below replaces the literal string $path with the contents of variable $usb

The only way I could get this to work under busybox ash is with completely bare \\$
to escape the literal $path in two separate chunks as \\$'path' which is REALLY weird.

root@zero:~# usb='/mnt/stick'; echo 'Path $path is it!' | sed -r 's|'\\$'path'"|$usb|g"
Path /mnt/stick is it!

It's great that it works because it allows me to pre-process my here-block before I
write it out to a file, but jeepers it would be nice to understand what's happening
and whether there are any other ways to do this under busybox with ash.

Here is the slightly simplified here-doc version which I actually use:

usb='/mnt/stick'
cat <<-'EOF' | sed -r 's|'\\$"path|$usb|g"
echo and here it is:
ftpdir=$path
echo more stuff
EOF

Best regards
Stepan Novotny



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