How to redirect Valgrind's output to a file?

Question

valgrind --log-file="filename"

By default, Valgrind writes its output to stderr. So you need to do something like:

valgrind a.out > log.txt 2>&1

Alternatively, you can tell Valgrind to write somewhere else; see http://valgrind.org/docs/manual/manual-core.html#manual-core.comment (but I've never tried this).

You can also set the options --log-fd if you just want to read your logs with a less. For example :

valgrind --log-fd=1 ls | less

In addition to the other answers (particularly by Lekakis), some string replacements can also be used in the option --log-file= as elaborated in the Valgrind's user manual.

Four replacements were available at the time of writing:

• %p: Prints the current process ID
  • valgrind --log-file="myFile-%p.dat" <application-name>
• %n: Prints file sequence number unique for the current process
  • valgrind --log-file="myFile-%p-%n.dat" <application-name>
• %q{ENV}: Prints contents of the environment variable ENV
  • valgrind --log-file="myFile-%q{HOME}.dat" <application-name>
• %%: Prints %
  • valgrind --log-file="myFile-%%.dat" <application-name>