Software & Apps Linux Understand Linux Command - Unix Command By Juergen Haas Writer Former Lifewire writer Juergen Haas is a software developer, data scientist, and a fan of the Linux operating system. our editorial process Juergen Haas Updated January 30, 2020 vgajic / Getty Images Linux Switching from Windows Tweet Share Email Man formats and displays the on-line manual pages. If you specify section, man only looks in that section of the manual. Name is normally the name of the manual page, which is typically the name of a command, function, or file. However, if name contains a slash (/) then man interprets it as a file specification so that you can do man ./foo.5 or even man /cd/foo/bar.1.gz. See below for a description of where man looks for the manual page files. Name man - format and display the on-line manual pagesmanpath - determine user's search path for man pages Synopsis man [-acdfFhkKtwW] [--path] [-m system] [-pstring] [-C config_file] [-M pathlist] [-P pager] [-Ssection_list] [section] name ... Options -C config_file Specify the configuration file to use; the default is /etc/man.config. (See man.conf(5).) -M path Specify the list of directories to search for man pages. Separate the directories with colons. An empty list is the same as not specifying -M at all. See SEARCH PATH FOR MANUAL PAGES. -P pager Specify which pager to use. This option overrides the MANPAGER environment variable, which in turn overrides the PAGER variable. By default, man uses /usr/bin/less -isr. -S section_list List is a colon-separated list of manual sections to search. This option overrides the MANSECTenvironment variable. -a By default, man will exit after displaying the first manual page it finds. Using this option forces man to display all the manual pages that match name, not just the first. -c Reformat the source man page, even when an up-to-date cat page exists. This can be meaningful if the cat page was formatted for a screen with a different number of columns, or if the preformatted page is corrupted. -d Don't actually display the man pages, but do print gobs of debugging information. -D Both display and print debugging info. -f Equivalent to whatis. -F or --preformat Format only - do not display. -h Print a one-line help message and exit. -k Equivalent to apropos. -K Search for the specified string in *all* man pages. Warning: this is probably very slow! It helps to specify a section. (Just to give a rough idea, on my machine this takes about a minute per 500 man pages.) -m system Specify an alternate set of man pages to search based on the system name given. -p string Specify the sequence of preprocessors to run before nroff or troff. Not all installations will have a full set of preprocessors. Some of the preprocessors and the letters used to designate them are: eqn (e), grap (g), pic (p), tbl (t), vgrind (v), refer (r). This option overrides the MANROFFSEQ environment variable. -t Use /usr/bin/groff -Tps -mandoc to format the manual page, passing the output tostdout. The output from /usr/bin/groff -Tps -mandoc may need to be passed through some filter or another before being printed. -w or --path Don't actually display the man pages, but do print the location(s) of the files that would be formatted or displayed. If no argument is given: display (on stdout) the list of directories that is searched by man for man pages. If manpath is a link to man, then "manpath" is equivalent to "man --path." -W Like -w, but print file names one per line, without additional information. This is useful in shell commands like man -aW man | xargs ls -l CAT Pages Man will try to save the formatted man pages, in order to save formatting time the next time these pages are needed. Traditionally, formatted versions of pages in DIR/manX are saved in DIR/catX, but other mappings from man dir to cat dir can be specified in /etc/man.config. No cat pages are saved when the required cat directory does not exist. No cat pages are saved when they are formatted for a line length different from 80. No cat pages are saved when man.conf contains the line NOCACHE. It is possible to make man suid to a user man. Then, if a cat directory has owner man and mode 0755 (only writable by man), and the cat files have owner man and mode 0644 or 0444 (only writable by man, or not writable at all), no ordinary user can change the cat pages or put other files in the cat directory. If man is not made suid, then a cat directory should have mode 0777 if all users should be able to leave cat pages there. The option -c forces reformatting a page, even if a recent cat page exists. Search Path for Manual Pages man uses a sophisticated method of finding manual page files, based on the invocation options and environment variables, the /etc/man.config configuration file, and some built-in conventions and heuristics. First of all, when the name argument to man contains a slash (/), man assumes it is a file specification itself, and there is no searching involved. But in the normal case where name doesn't contain a slash, man searches a variety of directories for a file that could be a manual page for the topic named. If you specify the -M pathlist option, pathlist is a colon-separated list of the directories that mansearches. If you don't specify -M but set the MANPATH environment variable, the value of that variable is the list of the directories that man searches. If you don't specify an explicit path list with -M or MANPATH, man develops its own path list based on the contents of the configuration file /etc/man.config. The MANPATH statements in the configuration file identify particular directories to include in the search path. Furthermore, the MANPATH_MAP statements add to the search path depending on your command search path (i.e. your PATH environment variable). For each directory that may be in the command search path, a MANPATH_MAP statement specifies a directory that should be added to the search path for manual page files. man looks at the PATH variable and adds the corresponding directories to the manual page file search path. Thus, with the proper use ofMANPATH_MAP, when you issue the command man xyz, you get a manual page for the program that would run if you issued the command xyz. In addition, for each directory in the command search path (we'll call it a "command directory") for which you do not have a MANPATH_MAP statement, man automatically looks for a manual page directory "nearby" namely as a subdirectory in the command directory itself or in the parent directory of the command directory. You can disable the automatic "nearby" searches by including a NOAUTOPATH statement in/etc/man.config. In each directory in the search path as described above, man searches for a file namedtopic.section, with an optional suffix on the section number and possibly a compression suffix. If it doesn't find such a file, it then looks in any subdirectories named manN or catN where N is the manual section number. If the file is in a catN subdirectory, man assumes it is a formatted manual page file (cat page). Otherwise, man assumes it is unformatted. In either case, if the filename has a known compression suffix (like .gz), man assumes it is gzipped. If you want to see where (or if) man would find the manual page for a particular topic, use the --path (-w) option. Use the man command (% man) to see how a command is used on your particular computer.