Thread: Why parsing the output of ls is considered unsafe?

This one bothers me a lot why ls command output is considred as unsafe?

Code:

ls -l | something
ls -l | command | do | get_output

Originally Posted by rockdalinux

This one bothers me a lot why ls command output is considred as unsafe?

Code:

ls -l | something
ls -l | command | do | get_output

it will NOT be "unsafe" if you know what you are doing. If you are parsing files, don't use ls -l because you might hit problems with files with spaces in their file names.

a lot depends also on what your "something" or "command" is.... what do you actually want to do?? describe the problem you are having.

The ls will display all files including newlines, commas, pipes and almost anything except for NUL (\0). By default ls separates its output with newline (\n). This is good, but imagine your filename has newline (\n) itself. This makes it pretty difficult to get filename safely, hence it is considered as unsafe. Also, some output fields in the ls command changes from UNIX to Linux oses. Try using while or for loop to get file list. Here is a common for loop I use (again as ghostdog74 said provide us more info as we cannot imagine your problem ):

Code:

find /path/to/dir -type f -print0 | while IFS= read -r -d '' file
do
  echo "Processing ${file}
done

While example:

Code:

find . -print0 | while read -d $'\0' file
do
  echo -v "$file"
done

See http://www.cyberciti.biz/tips/handli...s-in-bash.html

I never had problem coz I never had a blank or anything special in file name. But just now I tested with blank and other stuff and it did failed. I was comparing some file using ls and sending to our program written in python. thanks for sharing for and while loop. I will patch my script later on

There is no problem parsing the output of ls -l unless there is a newline in a filename. Whitespace is no problem.

Symlinks need to be treated specially.

Code:

ls -l |
 while read -r perms links owner group size month day time file
 do
   case $file in
     *\ -\>\ *) : parse link name and file name here ;;
   esac
   : do whatever
 done