CODEWITHSUNDEEP
unixprintingnullstdouttcsh
user1228191
user1228191

Reputation: 691

If command returns nothing, then print/echo a statement to STDOUT in csh shell

I grep for a word/pattern in a file, if such a pattern doesn't exist in a file, then I want to print/echo "-". Can we do this on command line in a single lined command?

grep word <file> | <command to return "-" if "word" not present in file>

Similarly if script returns nothing , echo "-"

python script.py | <command to return "-" if script returns nothing/NULL

Upvotes: 0

Views: 2631

Answers (2)

fork2execve
fork2execve

Reputation: 1650

If you want to check that there is no output for a command regardless of its returncode then you should check that there is no output, one way of doing that is:

 awk '{print} END {if (NR == 0) print "-"}'

So for example:

$ grep - /dev/null | awk '{print} END {if (NR == 0) print "-"}'
-
$ echo some output | awk '{print} END {if (NR == 0) print "-"}'
some output

Upvotes: 1

snoop
snoop

Reputation: 171

This can be done by following command:

grep word file.txt ||  echo "-"

If word is present in file then it will print the line from file else will print -.

If command is script then:

ret=`python script.py`; if [[ "$ret" ]];then echo "$ret"; else echo "-"; fi

Upvotes: 0

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