Linux man page entries | different types

31 Mar, 2018
The man page(manual page) is a documentation manual of different commands available in unix or unix like operating systems.
To check manual entry for any command use, man command_nameIn this article, I’m using command printf for my demonstrations.
man printf

Output:
PRINTF(1)                                                      User Commands                                                      PRINTF(1)

NAME
       printf - format and print data

SYNOPSIS
       printf FORMAT [ARGUMENT]...
       printf OPTION

DESCRIPTION
       Print ARGUMENT(s) according to FORMAT, or execute according to OPTION:

       --help display this help and exit

       --version
              output version information and exit

       FORMAT controls the output as in C printf.  Interpreted sequences are:

       \"     double quote

       \\     backslash

       \a     alert (BEL)

...

If you observe carefully the above output, the top line contains PRINTF(1), the 1 in braces is type of man entry. The number basically corresponds to section of the manual page.
The manual is split into 8 sections, which are(on Research Unix, BSD, macOS and Linux):
Let’s continue with the example of PRINTF, for all entries, try below command:
man -a printf

Output:
PRINTF(1)                                                      User Commands                                                      PRINTF(1)

NAME
       printf - format and print data

SYNOPSIS
       printf FORMAT [ARGUMENT]...
       printf OPTION

DESCRIPTION
       Print ARGUMENT(s) according to FORMAT, or execute according to OPTION:

       --help display this help and exit

       --version
              output version information and exit

       FORMAT controls the output as in C printf.  Interpreted sequences are:

       \"     double quote

...

When you type q to exit, the below text appears on terminal, press enter to continue to see another entry of printf
--Man-- next: printf(3) [ view (return) | skip (Ctrl-D) | quit (Ctrl-C) ]

Output continued:
PRINTF(3)                                                Linux Programmer's Manual                                                PRINTF(3)

NAME
       printf, fprintf, dprintf, sprintf, snprintf, vprintf, vfprintf, vdprintf, vsprintf, vsnprintf - formatted output conversion

SYNOPSIS
       #include 

       int printf(const char *format, ...);
       int fprintf(FILE *stream, const char *format, ...);
       int dprintf(int fd, const char *format, ...);
       int sprintf(char *str, const char *format, ...);
       int snprintf(char *str, size_t size, const char *format, ...);

       #include 

       int vprintf(const char *format, va_list ap);
       int vfprintf(FILE *stream, const char *format, va_list ap);

...

To check specific entry to printf or any other command, you can directly provide section number, for example:
man 3 printf

Output: It will show man entry corresponding to section 3 of printf.
Some useful man command options:1) -f option
man -f printf

Output:It will display the short description of printf, if available similar to
printf - format and print data

2) -k option
man -k printf

Output:It will search the short manual page descriptions for keywords and display any matches.
printf               (1)  - format and print data
printf               (1p)  - write formatted output
printf               (3)  - formatted output conversion
printf               (3p)  - print formatted output
printf [builtins]    (1)  - bash built-in commands, see bash(1)

3) -w optionIt prints the location of cat files that will be displayed rather than the content of files.
man -w printf

Output:
/usr/share/man/man1/printf.1.gz

4) -K optionIt will search for text in all manual pages.
man -K printf

Output:It will display all man entries containing printf keyword, and after each entry is display you can press enter for viewing second entry.For example:The below is prompted to view second entry for printf, you can either skip it or quit to terminate the command.
--Man-- next: git-show(1) [ view (return) | skip (Ctrl-D) | quit (Ctrl-C) ]

References :1) wiki/Man_page2) Man entry of man
linux-command
Linux-Unix
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