How to append custom string to error output and redirect it to a file

Question

Given:

An ffprobe command that detects duration of an mp4 video files on a remote host.

Expected:

Output of ffprobe is prefixed with custom string and redirected to a text file.

Problem:

Sometimes due to network error, ffprobe fails with some error message. I would like to capture that error, prefix it with a custom string and send it to a text file.

Example:

This command appends "ABC=55" to out.txt where 55 is the discovered duration:

ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 https://example.com/video.mp4' | awk '{print "ABC="$1}' 2>&1 >> out.txt

However, if that same command encounters a network error, instead of writing "ABC=Error message here", it writes noting to text file and shows that message in console.

Question

How do I tweak this part to capture execution errors, prefix them with "ABC=" and send to out.txt?

| awk '{print "ABC="$1}' 2>&1 >> out.txt

Thank you.

EDIT

This solved the problem:

2>&1 | awk '{print "ABC="$0}'

Kent · Accepted Answer · 2020-05-28 13:06:46Z

1

Give this a try:

ffprobe cmd... 2>&1|awk '{print "ABC="$1}' >output.txt

answered May 28, 2020 at 13:06

Kent

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2 Comments

temuri Over a year ago

"2>&1 | awk '{print "ABC="$0}'" fixed it. Had to use $0

Kent Over a year ago

@temuri I took the $1 just from your original codes, I have no idea which part do you really need (whole line vs the 1st field). However, it is irrelevant. The point here is, which stderr you should redirect.

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