How can I escape white space in a bash loop list?
Here is a simple solution which handles tabs and/or whitespaces in the filename. If you have to deal with other strange characters in the filename like newlines, pick another answer.
The test directory
ls -F test
Baltimore/ Cherry Hill/ Edison/ New York City/ Philadelphia/ cities.txt
The code to go into the directories
find test -type d | while read f ; do
echo "$f"
done
The filename must be quoted ("$f"
) if used as argument. Without quotes, the spaces act as argument separator and multiple arguments are given to the invoked command.
And the output:
test/Baltimore
test/Cherry Hill
test/Edison
test/New York City
test/Philadelphia
First, don't do it that way. The best approach is to use find -exec
properly:
# this is safe
find test -type d -exec echo '{}' +
The other safe approach is to use NUL-terminated list, though this requires that your find support -print0
:
# this is safe
while IFS= read -r -d '' n; do
printf '%q\n' "$n"
done < <(find test -mindepth 1 -type d -print0)
You can also populate an array from find, and pass that array later:
# this is safe
declare -a myarray
while IFS= read -r -d '' n; do
myarray+=( "$n" )
done < <(find test -mindepth 1 -type d -print0)
printf '%q\n' "${myarray[@]}" # printf is an example; use it however you want
If your find doesn't support -print0
, your result is then unsafe -- the below will not behave as desired if files exist containing newlines in their names (which, yes, is legal):
# this is unsafe
while IFS= read -r n; do
printf '%q\n' "$n"
done < <(find test -mindepth 1 -type d)
If one isn't going to use one of the above, a third approach (less efficient in terms of both time and memory usage, as it reads the entire output of the subprocess before doing word-splitting) is to use an IFS
variable which doesn't contain the space character. Turn off globbing (set -f
) to prevent strings containing glob characters such as []
, *
or ?
from being expanded:
# this is unsafe (but less unsafe than it would be without the following precautions)
(
IFS=$'\n' # split only on newlines
set -f # disable globbing
for n in $(find test -mindepth 1 -type d); do
printf '%q\n' "$n"
done
)
Finally, for the command-line parameter case, you should be using arrays if your shell supports them (i.e. it's ksh, bash or zsh):
# this is safe
for d in "$@"; do
printf '%s\n' "$d"
done
will maintain separation. Note that the quoting (and the use of $@
rather than $*
) is important. Arrays can be populated in other ways as well, such as glob expressions:
# this is safe
entries=( test/* )
for d in "${entries[@]}"; do
printf '%s\n' "$d"
done
find . -type d | while read file; do echo $file; done
However, doesn't work if the file-name contains newlines. The above is the only solution i know of when you actually want to have the directory name in a variable. If you just want to execute some command, use xargs.
find . -type d -print0 | xargs -0 echo 'The directory is: '