I can write:
X=""
if [ -f foo.txt ]; then
X=$(<foo.txt)
fi
but this is 4 lines. Is there a more compact way to express this logic?
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2 Answers
If you do just X=$(< foo.txt), X will be empty if the file doesn't exist, but you'll get an error message:
$ X=$(< foo.txt)
-bash: foo.txt: No such file or directory
If you want to suppress that (but also any other error message), you can redirect stderr to /dev/null:
{ X=$(< too.txt); } 2> /dev/null
X is in fact empty afterwards:
$ declare -p X
declare -- X="
5 Comments
Socowi
A bit less efficient but shorter to write
x=$(cat file 2>&-).
Charles Nicholson
Is X unset or empty in the failure case here?
Benjamin W.
@CharlesNicholson Empty.
Charles Nicholson
Cool, thanks! (will "accept" after the 5-minute cool-off expires). I notice you put a space after the < inside the $(<foo.txt) expression. Is that stylistic or functional?
Benjamin W.
@CharlesNicholson Purely stylistic. I like having blanks around my redirections, and the manual also has a blank there ;)
You may want to use this one lines using success/error after file existence check:
[[ -f foo.txt ]] && s=$(<foo.txt) || s=''
s=$(<foo.txt) will be executed if file exists otherwise s='' gets executed.
