While I find that we can read some manuals about Library calls (C library functions) & acsii in Linux. But I still do not find any manual about C precedence order so far.

So you can recommend other useful manual about C now. Thank you!

PS: Note that the manual can be accessed via man command in Linux, so do not take those online manual or books into answers please.


4 Answers 4


man libc covers standard C libraries (glibc, Linux libc) on Linux.

In "SEE ALSO" section, there are

syscalls(2), feature_test_macros(7), man-pages(7), standards(7)

You can look into the details by

man 2 syscalls

man 7 feature_test_macros

man 7 man-pages

man 7 standards


Not as man pages as far as I know, but there is cppreference-doc (apt install cppreference-doc-en-html, or ... cppreference-doc-en-qch if you use KDE), which is a packaged version of the C/C++ reference wiki (see for example its page on typedef).

The C and C++ sections are separate, so it is possible to use this as a C reference only.

  • That's 150MB and it's for C++. I'd prefer not have to learn the difference between C and C++. I have no interest in C++. Is there a similar C reference on the Net?
    – user147505
    Jun 19, 2018 at 13:33
  • 1
    The C and C++ sections are separate, you can avoid the C++ parts. There is a similar C reference on the Internet, it’s the same web site (go here to only see C). Jun 19, 2018 at 13:38

you can search with -k such as:

mohsen@debian:~/codes/amlak/amlak/src$ man -k socket
accept (2)           - accept a connection on a socket
accept4 (2)          - accept a connection on a socket
bind (2)             - bind a name to a socket
bindresvport (3)     - bind a socket to a privileged IP port
BIO_new_socket (3ssl) - socket BIO
BIO_s_socket (3ssl)  - socket BIO
connect (2)          - initiate a connection on a socket
dbus-cleanup-sockets (1) - clean up leftover sockets in a directory
filan (1)            - Multipurpose relay (SOcket CAT)
fuser (1)            - identify processes using files or sockets
getpeername (2)      - get name of connected peer socket
getsockname (2)      - get socket name
getsockopt (2)       - get and set options on sockets
gpsdctl (8)          - tool for sending commands to gpsd over its control socket
IO::Socket::INET6 (3pm) - Object interface for AF_INET|AF_INET6 domain sockets
IO::Socket::SSL (3pm) - - SSL sockets with IO::Socket interface
IO::Socket::SSL::Intercept (3pm) - - SSL interception (man in the middle)
IO::Socket::SSL::Utils (3pm) - - loading, storing, creating certificates and keys
irw (1)              - sends data from Unix domain socket to stdout
lircd (8)            - LIRC daemon decodes infrared signals and provides them on a Unix domain socket.
listen (2)           - listen for connections on a socket
ncat (1)             - Concatenate and redirect sockets
Net::SSL (3pm)       - support for Secure Sockets Layer
Net::SSLeay::Handle (3pm) - Perl module that lets SSL (HTTPS) sockets be handled as standard file handles.
procan (1)           - Multipurpose relay (SOcket CAT)
raw (7)              - Linux IPv4 raw sockets
recv (2)             - receive a message from a socket
recvfrom (2)         - receive a message from a socket
recvmmsg (2)         - receive multiple messages on a socket
recvmsg (2)          - receive a message from a socket
rtnetlink (7)        - Linux IPv4 routing socket
send (2)             - send a message on a socket
sendmmsg (2)         - send multiple messages on a socket
sendmsg (2)          - send a message on a socket
sendto (2)           - send a message on a socket
setsockopt (2)       - get and set options on sockets
socat (1)            - Multipurpose relay (SOcket CAT)
sockatmark (3)       - determine whether socket is at out-of-band mark
socket (2)           - create an endpoint for communication
socket (7)           - Linux socket interface
socketcall (2)       - socket system calls
socketpair (2)       - create a pair of connected sockets
ss (8)               - another utility to investigate sockets
systemd-udevd-control.socket (8) - Device event managing daemon
systemd-udevd-kernel.socket (8) - Device event managing daemon
unix (7)             - sockets for local interprocess communication
unixcmd (1)          - Simple remote command for unix sockets
unixterm (1)         - (simple) Remote terminal for unix sockets
vdeterm (1)          - (simple) Remote terminal for vde management sockets
vfs_smb_traffic_analyzer (8) - log Samba VFS read and write operations through a socket to a helper application
watchgnupg (1)       - Read and print logs from a socket
X11::Protocol::Connection::INETSocket (3pm) - Perl module for IO::Socket::INET-based X11 connections
X11::Protocol::Connection::Socket (3pm) - Perl module base class for IO::Socket-based X11 connections
X11::Protocol::Connection::UNIXSocket (3pm) - Perl module for IO::Socket::UNIX-based X11 connections

You see a number front of each man page, man pages categorized by level :

   1   Executable programs or shell commands
   2   System calls (functions provided by the kernel)
   3   Library calls (functions within program libraries)
   4   Special files (usually found in /dev)
   5   File formats and conventions eg /etc/passwd
   6   Games
   7   Miscellaneous (including macro packages and conventions), e.g. man(7), groff(7)
   8   System administration commands (usually only for root)
   9   Kernel routines [Non standard]

I think you can find your api by your level, oh by the way , man -a youmanpage, show your manpage in all level

for example man strtok

man -a passwd : show passwd command and /etc/passwd format


The GNU C Library Reference Manual is a comprehensive manual with regards to the ISO C standard, as well as additional features specific to POSIX and other derivatives of the Unix operating system, and extensions specific to GNU systems.

You can also look up the manual pages of any GNU C Library functions online.

  • I means man which are built in Linux, not these online manual...
    – acgtyrant
    Oct 17, 2013 at 7:17
  • It was better you can introduce GNU reference instead of just man page, you named libc.pdf. Oct 18, 2013 at 3:21

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