Some help, please!
Some people may think this is unimportant, while others consider it important. For me, it is essential. What if we do not know what a command does, how to use it, or which parameters a file accepts? We might search the Internet to learn how to use or configure it—but what if we have no Internet connection? That is frustrating. Knowing the basics of the help tools can be useful in such situations, so let us begin.
- whatis …
This command tells us what another command does. For example, to find out what ls is:
$ whatis ls
ls (1) - list directory contents <= the answer
- —help
This shows the required parameters and available options. For example:
$ ls —help
Usage: ls [OPTION]… [FILE]…
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuSUX nor #sort.
Mandatory arguments to long options are mandatory for short options too.
-a, #all do not hide entries starting with .
-A, #almost-all do not list implied . and ..
#author print the author of each file
-b, #escape print octal escapes for nongraphic characters
#block-size=SIZE use SIZE-byte blocks
-B, #ignore-backups do not list implied entries ending with ~
-c with -lt: sort by, and show, ctime (time of last
modification of file status information)
with -l: show ctime and sort by name
otherwise: sort by ctime
-C list entries by columns
#color[=WHEN] control whether color is used to distinguish file
types. WHEN may be never', always’, or auto' -d, #directory list directory entries instead of contents, and do not dereference symbolic links -D, #dired generate output designed for Emacs' dired mode -f do not sort, enable -aU, disable -lst -F, #classify append indicator (one of \*/=@|) to entries #format=WORD across -x, commas -m, horizontal -x, long -l, single-column -1, verbose -l, vertical -C #full-time like -l #time-style=full-iso -g like -l, but do not list owner -G, #no-group inhibit display of group information -h, #human-readable print sizes in human readable format (e.g., 1K 234M 2G) #si likewise, but use powers of 1000 not 1024 -H, #dereference-command-line follow symbolic links listed on the command line #dereference-command-line-symlink-to-dir follow each command line symbolic link that points to a directory #indicator-style=WORD append indicator with style WORD to entry names: none (default), classify (-F), file-type (-p) -i, #inode print index number of each file -I, #ignore=PATTERN do not list implied entries matching shell PATTERN -k like #block-size=1K -l use a long listing format -L, #dereference when showing file information for a symbolic link, show information for the file the link references rather than for the link itself -m fill width with a comma separated list of entries -n, #numeric-uid-gid like -l, but list numeric UIDs and GIDs -N, #literal print raw entry names (don't treat e.g. control characters specially) -o like -l, but do not list group information -p, #file-type append indicator (one of /=@|) to entries -q, #hide-control-chars print ? instead of non graphic characters #show-control-chars show non graphic characters as-is (default unless program is ls’ and output is a terminal)
-Q, #quote-name enclose entry names in double quotes
#quoting-style=WORD use quoting style WORD for entry names:
literal, locale, shell, shell-always, c, escape
-r, #reverse reverse order while sorting
-R, #recursive list subdirectories recursively
-s, #size print size of each file, in blocks
-S sort by file size
#sort=WORD extension -X, none -U, size -S, time -t,
version -v
status -c, time -t, atime -u, access -u, use -u
#time=WORD show time as WORD instead of modification time:
atime, access, use, ctime or status; use
specified time as sort key if #sort=time
#time-style=STYLE show times using style STYLE:
full-iso, long-iso, iso, locale, +FORMAT
FORMAT is interpreted like date'; if FORMAT is FORMAT1FORMAT2, FORMAT1 applies to non-recent files and FORMAT2 to recent files; if STYLE is prefixed with posix-’, STYLE
takes effect only outside the POSIX locale
-t sort by modification time
-T, #tabsize=COLS assume tab stops at each COLS instead of 8
-u with -lt: sort by, and show, access time
with -l: show access time and sort by name
otherwise: sort by access time
-U do not sort; list entries in directory order
-v sort by version
-w, #width=COLS assume screen width instead of current value
-x list entries by lines instead of by columns
-X sort alphabetically by entry extension
-1 list one file per line
SELINUX options:
#lcontext Display security context. Enable -l. Lines
will probably be too wide for most displays.
-Z, #context Display security context so it fits on most
displays. Displays only mode, user, group,
security context and file name.
#scontext Display only security context and file name.
#help display this help and exit
#version output version information and exit
SIZE may be (or may be an integer optionally followed by) one of following:
kB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T, P, E, Z, Y.
By default, color is not used to distinguish types of files. That is
equivalent to using #color=none. Using the #color option without the
optional WHEN argument is equivalent to using #color=always. With
#color=auto, color codes are output only if standard output is connected
to a terminal (tty).
Report bugs to .
Wow, that is a lot of output! Still, it helps us know which values to enter to get the correct behavior and the result we want.
