[SOLVED] how to escape $ (dollar sign) when echoing environment variable

lvm_ · 05-03-2024, 02:20 AM

Quote:

Originally Posted by mfoley

Single quotes as lvm_ suggested can't be used because the $REPLY would not be substituted with its value.

Not here, earlier - in assignment. variable='file$name', not '$variable'. Have you ever wondered why ls puts single quotes around tricky file names? That's the reason.

wpeckham · 05-03-2024, 01:28 PM

BASH has some lovely string editing features that might be leveraged to convert or eliminate the special characters that are causing your headaches.

If that might help.

mfoley · 05-06-2024, 05:30 PM

Quote:

Originally Posted by MadeInGermany

For reading file names use IFS= and -r
Use the built-in string operators (parameter modifiers).

Code:

while IFS= read -r fn
do
   x=${fn/\/mnt/} # deletes(substitutes) the first occurrence of /mnt (like sed 's#/mnt##')
#   x=${fn/#\/mnt/} # deletes(substitutes) a /mnt at the beginning (like sed 's#^/mnt##')
#   x=${fn#/mnt} # deletes a /mnt at the beginning (like sed 's#^/mnt##')
    if [ -e "$x" ]; then echo yup; else echo nope; fi
done < fileList

If you must use sed then this is almost safe:

Code:

x=$(echo "$fn" | sed 's#/mnt##')

Exception: $fn is a echo option like -n or -e
100% safe is printf with a format:

Code:

x=$(printf "%s\n" "$fn" | sed 's#/mnt##')

$-expressions within " " (like "$fn") are evaluated/substituted; no further substitution or expansion happens.
An assignment (like x=val) does not need quotes (x="val"). But a command does:

Code:

printf "%s\n" "$(printf "%s\n" "$fn" | sed 's#/mnt##')"

$( ) is a sub shell; the quotes in it don't interfere with the main shell.
For demonstration, you could write it as

Code:

printf "%s\n" "$(
# sub shell starts
printf "%s\n" "$fn" | sed 's#/mnt##'
# sub shell ends
)"

Thanks MadeInGermany! All those suggested ideas worked for my example. I appreciate you addressing the actual question and giving a solution!! I will investigate that "while IFS= read -r fn" construct further to see how that works.