CODEWITHSUNDEEP
linuxbashshellscripting
tgmdbm
tgmdbm

Reputation: 1563

Prevent 'cp' from outputting the file name from a bash script

I have a shell script which copies a few files to the current directory, compresses them, and streams the compressed file to stdout.

On the client side I use plink to execute the script and stream stdin to a file.

This almost works.

It seems that the cp command outputs the file name being copied when its executed from inside the script. If I execute 'cp /path/to/file1 .' in the shell it does it quietly; if I execute it in a script it outputs "file1".

How do I prevent this? I've tried piping the output of the cp command to /dev/null and to a dummy text file but with no luck.

thanks for any help.

the script

#!/bin/bash

cp /path/to/file1 .
cp /path/to/file2 .
cp /path/to/file3 .

tar -cvzf package.tgz file1 file2 file3

cat package.tgz

the output

file1
file2
file3
<<binary data>>

Upvotes: 0

Views: 1617

Answers (3)

bigendian
bigendian

Reputation: 818

As others pointed out, the -v (verbose) option to tar is kicking out the file names to STDERR. You can also make your script more efficient by having tar write the compressed file stream to STDOUT:

tar zcf - file1 file2 file3

In this example, the "-" option passed as the filename makes tar write the output to STDOUT.

Upvotes: 0

bendin
bendin

Reputation: 9574

Aha! I'd always assumed that the file names emitted by tar go to stderr, but that isn't always the case: only if you write your tar file to stdout do the files written by -v go to stderr:

$ tar cvf - share > /dev/null
share/                         # this must be going
share/.DS_Store                # to stderr since we
share/man/                     # redirected stdout to
share/man/.DS_Store            # /dev/null above.
share/man/man1/
share/man/man1/diffmerge.man1

The counter-example:

$ tar cvf blah.tar share > /dev/null

This produced no list of file names because they got sent to /dev/null. I guess you learn something new every day. :-)

Upvotes: 2

CesarB
CesarB

Reputation: 45545

It's not cp, it's tar. You are passing it -v, which makes it print the names of the files.

Upvotes: 19

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