cmd bash "cat" behaves differently when is added to variable

bryn1u · 07-23-2021, 07:40 AM

Hey guys,

Im trying to use cat which is assigned to variable. But the output of "cat" is differently then from command line, why ?

Code:

root@Proton:[~]:#> cat text
dupufufr3
frerfr3
3r
edziopedzio
frwnfru
fjwlfrew
fklwkfw
fkwf

root@Proton:[~]:#> variable="$(cat text)"
root@Proton:[~]:#> echo $variable
dupufufr3 frerfr3 3r edziopedzio frwnfru fjwlfrew fklwkfw fkwf

Why this is interpreted differently ? How can i get the same output as from command line ?

Thank you,

MadeInGermany · 07-23-2021, 10:39 AM

Because the shell further expands unquoted $variables in command arguments (and in for lists).

Code:

variable=$(cat text) # assignment: no further expansions aftet $-substitution
echo "$variable" # quotes permit $-substitution but no further expansions

The further expansions are
1. field splitting (using $IFS, InputFieldSeparator)
2. filename generation (e.g. if $variable has * wildcards).

shruggy · 07-23-2021, 01:30 PM

I'll add that cat behaves the same. It's echo that makes the difference.

From the GNU Bash manual:

Quote:

echo

Code:
echo [-neE] [arg …]
Output the args, separated by spaces, terminated with a newline.

ondoho · 07-24-2021, 04:31 AM

also "$variable" might show different results to $variable.