Redirection of output results in an empty file

Question

I have a shell script that I should preferably not be editing but that I would have to use the output of. Doing ./SomeScript.sh -d displays the output I need on the shell.

However, I get an empty file if I try to redirect the output.

./SomeScript.sh -d > temp 
cat temp

After checking Why redirecting output sometimes produces an empty file?, I have also tried echo $(./SomeScript.sh -d) but the command prints nothing.

Initially I was trying to grep a line from the output, but after realising that nothing was returned, I tried to redirect the output to a file instead and realised this problem. Any idea why this might be happening?

Answer 1

If ./SomeScript.sh -d > temp results in an empty file (and yet you can see the output on the screen), that means that the program is maybe printing to stderr instead of stout. So, try redirecting its stderr too -- i.e., use this:

./SomeScript.sh -d >temp 2>&1

Or you could send the outputs to two separate files:

./myScript  1>outtemp 2>errtemp 

Answer 2

Use

./SomeScript.sh -d >> temp

this will append each line of the script, rather than write and overwrite line by line.

Edit: try

./SomeScript.sh -d &>> temp

if you want to redirect stderr as well as stdout.

Answer 3

script -c "./SomeScript.sh -flags" temp

This command worked for me but I'm not too sure why either.

Answer 4

I faced the same issue and came for this workaround:

./SomeScript.sh -d | tee temp.txt

Hope it saves you time!