nl stdout

huhp · 2017-10-02 13:05:58

Anyone else realized that nl's output isn't redirected?
For example

nl > file.txt

and

nl | cat -

fail to produce any output, while

cat file1.txt | nl > file2.txt

does work, so maybe it's because I pressed ^C (even though it works fine with cat)?
However, even weirder is

nl | head -2

which doesn't quit automatically after 2 lines like

cat - | head -2

would.

Any idea how to works around this?

ayekat · 2017-10-02 13:26:37

nl counts the number of lines in a text file, if one is provided on the command line, otherwise it reads from standard input.

You should not press ^C in such a case, but ^D, to send an End of Transmission (EOT). Before you do that, nl will not count any lines.

You may want to read up on how shell redirection and stdin/stdout/stderr work, e.g. https://en.wikipedia.org/wiki/Redirection_(computing)

WorMzy · 2017-10-02 13:27:38

You need to send an EOF (Ctrl+d) to terminate the input, not an interrupt signal (Ctrl+c).

Alternatively use a HEREDOC.

EDIT: snaked by ayecat

Last edited by WorMzy (2017-10-02 13:28:07)

HalosGhost · 2017-10-02 13:33:18

if you use the first or second command, but end input with ^D (EOT) rather than ^C (fire SIGINT), you will find it properly writes to the file.

I was ninja'd.

All the best,

-HG

Last edited by HalosGhost (2017-10-02 13:33:57)

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