man 2 read # 查看系统调用read
man 3 fread # 查看库函数read
熟悉man man很重要，你能找到你要的everything.
MAN(1) Manual pager utils MAN(1) NAME man - an interface to the on-line reference manuals SYNOPSIS man [-C file] [-d] [-D] [--warnings[=warnings]] [-R encoding] [-L locale] [-m system[,...]] [-M path] [-S list] [-e extension] [-i|-I] [--regex|--wildcard] [--names-only] [-a] [-u] [--no-subpages] [-P pager] [-r prompt] [-7] [-E encoding] [--no-hyphenation] [--no-justification] [-p string] [-t] [-T[device]] [-H[browser]] [-X[dpi]] [-Z] [[section] page ...] ... man -k [apropos options] regexp ... man -K [-w|-W] [-S list] [-i|-I] [--regex] [section] term ... man -f [whatis options] page ... man -l [-C file] [-d] [-D] [--warnings[=warnings]] [-R encoding] [-L locale] [-P pager] [-r prompt] [-7] [-E encoding] [-p string] [-t] [-T[device]] [-H[browser]] [-X[dpi]] [-Z] file ... man -w|-W [-C file] [-d] [-D] page ... man -c [-C file] [-d] [-D] page ... man [-?V] DESCRIPTION man is the system's manual pager. Each page argument given to man is normally the name of a program, utility or function. The manual page associated with each of these arguments is then found and displayed. A section, if provided, will direct man to look only in that section of the manual. The default action is to search in all of the available sections, following a pre-defined order and to show only the first page found, even if page exists in several sections. The table below shows the section numbers of the manual followed by the types of pages they contain. 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] A manual page consists of several sections.
很多文档在系统调用上写着xxx(N)，其中的N就是指linux编程手册的哪一册。
如果不知道在哪一册，可以通过man -k myfunc查包含myfunc的各系统调用、库函数、命令行或其他。如下：
[zjh@lightdb1 ~]$ man -k getcwd man: can't set the locale; make sure $LC_* and $LANG are correct getcwd (2) - get current working directory getcwd (3) - get current working directory getcwd (3p) - get the pathname of the current working directory Tcl_FSGetCwd (3) - procedures to interact with any filesystem Tcl_GetCwd (3) - manipulate the current working directory
跟yum search一样，很先进。