I found this accidentally.

I just typed man fork, and instead of showing the system call documentation, it showed to me an awk extension, however, the section page number was 3am, instead of just 3.

What does 3am means?


2 Answers 2


It appears to be the manual page for a GNU Awk (gawk) extension module. The complete list is:

$ find /usr/share/man/man3 -name '*3am*' | xargs dpkg -S
gawk: /usr/share/man/man3/readfile.3am.gz
gawk: /usr/share/man/man3/inplace.3am.gz
gawk: /usr/share/man/man3/ordchr.3am.gz
gawk: /usr/share/man/man3/revoutput.3am.gz
gawk: /usr/share/man/man3/readdir.3am.gz
gawk: /usr/share/man/man3/filefuncs.3am.gz
gawk: /usr/share/man/man3/revtwoway.3am.gz
gawk: /usr/share/man/man3/time.3am.gz
gawk: /usr/share/man/man3/rwarray.3am.gz
gawk: /usr/share/man/man3/fork.3am.gz
gawk: /usr/share/man/man3/fnmatch.3am.gz

I would guess the am stands for awk module.

  • 1
    In general, section 3 of the manual contains entries for library calls, which seems appropriate for gawk libraries, whereas fork() is carried out by the kernel and is therefore documented in section 2.
    – Kusalananda
    Mar 25, 2019 at 13:30
  • 2
    Yeah it seems that some libraries or "man page extensions" adds a postfix to the man page section number. In my system I've some prefixes like cpp, ssl or perl. Mar 25, 2019 at 15:09

If you read the middle part of the first line output by man 3am readfile, you'll see:

GNU Awk Extension Modules

Now shouldn't be hard to guess from here, specifically when comparing to other first lines.

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