Linux, write output to file, including the command

Question

How can I write into a file the output of a command but also include the command at the beginning of a file?

eg:

grep -nrs 'blah' . >/home/ca/out.txt

so that the file shows

grep -nrs 'blah' . >/home/ca/out.txt
./something.cpp:1329:    if(blah)

to leave a blank line between?

grep -nrs 'blah' . >/home/ca/out.txt

./something.cpp:1329:    if(blah)
....

Thank you

Answer 1

You can store command line and result both in a file using bash -vc like this:

bash -vc "grep -nrs 'blah' ." >& /home/ca/out.txt

• -v is for verbose mode in bash that outputs full command before executing it.
• -c is for running a command from command line
• >& is for redirecting both stdout and stderr

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Another approach is store command line in an array:

arr=(grep -nrs 'blah' .)
{ printf "%q " "${arr[@]}"; echo; echo; "${arr[@]}"; } >& /home/ca/out.txt

Answer 2

You can use logsave (usage) to log the output together with a timestamp and the command, e.g.:

logsave -a output.txt ls

Saves the output of the ls command into output.txt:

Log of ls 
Thu Jan 29 16:49:25 2015

[output of command]

Thu Jan 29 16:49:25 2015
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