Bash: Subshell behaviour of ls

Question

I am wondering why I do not get se same output from:

ls -1 -tF | head -n 1

and

echo $(ls -1 -tF | head -n 1)

I tried to get the last modified file, but using it inside a sub shell sometimes I get more than one file as result?

Why that and how to avoid?

Answer 1

The problem arises because you are using an unquoted subshell and -F flag for ls outputs shell special characters appended to filenames.

-F, --classify
append indicator (one of */=>@|) to entries

Executable files are appended with *.

When you run

echo $(ls -1 -tF | head -n 1)

then

$(ls -1 -tF | head -n 1)

will return a filename, and if it happens to be an executable and also be the prefix to another file, then it will return both.

For example if you have

test.sh
test.sh.backup

then it will return

test.sh*

which when echoed expands to

test.sh test.sh.backup

Quoting the subshell prevents this expansion

echo "$(ls -1 -tF | head -n 1)"

returns

test.sh*