5

Scenario:

$ ls -1
'x y.pdf'

$ ls -1 | cat
x y.pdf

Here we see that surrounding single quotes are missing if output of ls -1 is passed to a pipe. Why does this happen? How to keep the surrounding single quotes?

There is a -Q option:

$ man ls | grep quote
       -Q, --quote-name
              enclose entry names in double quotes

However, it encloses entry names in double quotes.

pmor
  • 464

1 Answers1

12

Why does this happen?

The maintainers of GNU Coreutils's ls have decided so. The program checks whether its output is a terminal and applies different output formatting (colors, special characters, etc).

For example, it also doesn't suppress "non-printable" characters when output is not a terminal, under the assumption that it's going to be processed by a script and not merely looked at. (Not recommended in many cases but valid in some cases, and the program does specifically account for that.) The quoting-by-default is new but having ls automatically disable it for non-tty output is the same as before.

How to keep the surrounding single quotes?

Use --quoting-style=shell if the names are about to be used as input for a sh/bash command.

But if you're planning to use the output as part of a shell script, consider whether ls is necessary at all. For example, far too often for x in $(ls *.c) is misused when for x in *.c would do a better job.

grawity
  • 501,077