CODEWITHSUNDEEP
grepstderrpiping
mareks
mareks

Reputation: 491

Piping error messages with grep

I have a script that fails because some files are missing.

Running the script and piping it to grep 

$ ./adder | grep Error

produces the following output:

Error in <TFile::ReadBuffer>: error reading all requested bytes from file v2.2_V3_194424_194712/output_853.root, got 0 of 300
Error in <TFile::Init>: v2.2_V3_194424_194712/output_853.root not a ROOT file

and similar output with different files

I'd like to extract the root files like v2.2_V3_194424_194712/output_853.root from this output, but doing ./adder | grep Error | grep .root doesn't work.

Why is that?

Upvotes: 4

Views: 10927

Answers (2)

Steve
Steve

Reputation: 54572

Like piokuc's suggests, combine stderr with stdout. However, I think you are looking a better invocation of grep:

./adder 2>&1 | grep "^Error" | grep -oP '[^ ]*\.root'

Upvotes: 4

piokuc
piokuc

Reputation: 26204

You need to redirect standard error stream (numeric code: 2) from first command in the pipe to standard output stream (numeric code: 1), like this:

$ ./adder 2>&1 | grep Error

Upvotes: 7

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