[SOLVED] Why does $IFS contain '$' only

dmiraj · 12-18-2021, 03:20 PM

Hello all,
When issuing the following command

Code:

cat -A <(echo $IFS)

. The output is $ . But this is not what $IFS is supposed to be,as indicated in the man page:

Code:

<space><tab><newline>

.

So why is it equal to $, but word splitting happens just fine.

I am using Ubuntu.

Thank you.

smallpond · 12-18-2021, 03:38 PM

The bash man page says <space><tab><newline> is the default value, which is the value when IFS is not set.

enigma9o7 · 12-18-2021, 04:00 PM

It doesn't. You put -A switch onto cat which makes it display $ on every line.

Code:

cat --help

says

Code:

  -A, --show-all           equivalent to -vET
  -b, --number-nonblank    number nonempty output lines, overrides -n
  -e                       equivalent to -vE
  -E, --show-ends          display $ at end of each line
  -n, --number             number all output lines
  -s, --squeeze-blank      suppress repeated empty output lines
  -t                       equivalent to -vT
  -T, --show-tabs          display TAB characters as ^I
  -u                       (ignored)
  -v, --show-nonprinting   use ^ and M- notation, except for LFD and TAB

Since -A does -vET and -E prints a $ on every line, you get your $

boughtonp · 12-18-2021, 04:43 PM

It's showing "$" because you haven't quoted the variable and so the evaluated command being run is "cat -A <(echo)" and the echo is outputting a newline character.

If you quote the variable you will get the contents of it included in the command, and if you use -n option you can prevent echo outputting the trailing newline character, i.e:

Code:

$ cat -A <(echo -n "$IFS")
 ^I$

dmiraj · 12-26-2021, 07:56 AM

Quote:

Originally Posted by boughtonp

It's showing "$" because you haven't quoted the variable and so the evaluated command being run is "cat -A <(echo)" and the echo is outputting a newline character.

If you quote the variable you will get the contents of it included in the command, and if you use -n option you can prevent echo outputting the trailing newline character, i.e:

Code:

$ cat -A <(echo -n "$IFS")
 ^I$

Thank you, this makes sense to me now.