Man page section numbers
In Linux documentation, commands are often followed by a number in parentheses, like grep(1) or mount(8). That number refers to a specific section of the man pages, which are organized by the type of content they describe:
| Section | Description | Examples |
|---|---|---|
| 1 | User commands: Executable programs available in user environments (usually in $PATH). | ls(1), grep(1) |
| 2 | System call interfaces: Low-level functions that transfer control to the kernel. Some correspond to actual syscalls (like read); others (like fork) are wrappers around internal syscalls (e.g. clone). | open(2), read(2), fork(2) |
| 3 | Library functions: APIs provided by user-space libraries like libc, libm, etc. | printf(3), malloc(3) |
| 4 | Special files: Interfaces to device files, usually found under /dev. | null(4), random(4) |
| 5 | File formats and config files: Syntax and conventions for text-based configuration. | fstab(5), passwd(5) |
| 6 | Games and amusements: Games, screensavers, and recreational software. | fortune(6) |
| 7 | Miscellaneous: Conventions, standards, protocols, charsets, signal descriptions, etc. | signal(7), man(7) |
| 8 | System administration commands: Tools for sysadmins; often require root privileges. | mount(8), iptables(8) |
Why this matters? Sometimes, the same name appears in more than one section. A classic example:
passwd(1)– the command you run to change your passwordpasswd(5)– the configuration file/etc/passwd
So when you want a specific version, you can tell man which section to open:
man 5 passwd
This will skip the default (usually section 1) and go straight to section 5.
If you’re unsure which sections are available for a command, use:
man -f <command>
or equivalently
whatis <command>
This is handy and it also displays one-line descriptions of commands.