# Command Line Arguments and Options * Some options can be specified by a single dash and a single character, other options require two dashes and a multi-character (verbose) description. * Formats can also be combined, by following some rules: * one character options can be merged * multi-character formats cannot be combined ## ls command example ```bash ls --help Usage: ls [OPTION]... [FILE]... List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor --sort is specified. Mandatory arguments to long options are mandatory for short options too. -a, --all do not ignore entries starting with . -A, --almost-all do not list implied . and .. [...] -I, --ignore=PATTERN do not list implied entries matching shell PATTERN -k, --kibibytes default to 1024-byte blocks for disk usage; used only with -s and per directory totals -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 user and group IDs [...] ``` * **`ls -al`** - Single character options: ```bash ls -al total 100 drwxr-x--- 16 user user 4096 ago 28 15:15 . drwxr-xr-x 3 root root 4096 lug 24 15:19 .. -rw------- 1 user user 829 ago 8 10:44 .bash_history -rw-r--r-- 1 user user 220 lug 24 15:19 .bash_logout -rw-r--r-- 1 user user 3771 lug 24 15:19 .bashrc drwx------ 12 user user 4096 ago 28 14:41 .cache drwx------ 12 user user 4096 ago 28 14:41 .config drwxr-xr-x 2 user user 4096 lug 24 15:37 Desktop drwxr-xr-x 2 user user 4096 lug 24 15:37 Documents drwxr-xr-x 3 user user 4096 lug 24 15:59 Downloads drwx------ 2 user user 4096 ago 28 15:38 .gnupg -rw------- 1 user user 20 ago 28 15:15 .lesshst drwx------ 3 user user 4096 lug 24 15:37 .local drwxr-xr-x 2 user user 4096 lug 24 15:37 Music drwxr-xr-x 2 user user 4096 lug 24 15:37 Pictures -rw-r--r-- 1 user user 807 lug 24 15:19 .profile drwxr-xr-x 2 user user 4096 lug 24 15:37 Public drwx------ 4 user user 4096 lug 24 15:59 snap drwx------ 2 user user 4096 lug 24 15:40 .ssh -rw-r--r-- 1 user user 0 lug 24 15:37 .sudo_as_admin_successful drwxr-xr-x 2 user user 4096 lug 24 15:37 Templates -rw-r----- 1 user user 5 ago 28 14:41 .vboxclient-clipboard.pid -rw-r----- 1 user user 5 ago 28 14:41 .vboxclient-display-svga-x11.pid -rw-r----- 1 user user 5 ago 28 14:41 .vboxclient-draganddrop.pid -rw-r----- 1 user user 5 ago 28 14:41 .vboxclient-seamless.pid drwxr-xr-x 2 user user 4096 lug 24 15:37 Videos ``` * **`ls --all -l`** - Multi character options: ```bash # Same output ls --all -l total 100 drwxr-x--- 16 user user 4096 ago 28 15:15 . drwxr-xr-x 3 root root 4096 lug 24 15:19 .. -rw------- 1 user user 829 ago 8 10:44 .bash_history -rw-r--r-- 1 user user 220 lug 24 15:19 .bash_logout -rw-r--r-- 1 user user 3771 lug 24 15:19 .bashrc drwx------ 12 user user 4096 ago 28 14:41 .cache drwx------ 12 user user 4096 ago 28 14:41 .config drwxr-xr-x 2 user user 4096 lug 24 15:37 Desktop drwxr-xr-x 2 user user 4096 lug 24 15:37 Documents drwxr-xr-x 3 user user 4096 lug 24 15:59 Downloads drwx------ 2 user user 4096 ago 28 15:38 .gnupg -rw------- 1 user user 20 ago 28 15:15 .lesshst drwx------ 3 user user 4096 lug 24 15:37 .local drwxr-xr-x 2 user user 4096 lug 24 15:37 Music drwxr-xr-x 2 user user 4096 lug 24 15:37 Pictures -rw-r--r-- 1 user user 807 lug 24 15:19 .profile drwxr-xr-x 2 user user 4096 lug 24 15:37 Public drwx------ 4 user user 4096 lug 24 15:59 snap drwx------ 2 user user 4096 lug 24 15:40 .ssh -rw-r--r-- 1 user user 0 lug 24 15:37 .sudo_as_admin_successful drwxr-xr-x 2 user user 4096 lug 24 15:37 Templates -rw-r----- 1 user user 5 ago 28 14:41 .vboxclient-clipboard.pid -rw-r----- 1 user user 5 ago 28 14:41 .vboxclient-display-svga-x11.pid -rw-r----- 1 user user 5 ago 28 14:41 .vboxclient-draganddrop.pid -rw-r----- 1 user user 5 ago 28 14:41 .vboxclient-seamless.pid drwxr-xr-x 2 user user 4096 lug 24 15:37 Videos ``` * **`ls -I`** - use ignore pattern option: ```bash # Ignore all entries that starts with the letter D: ls -I "D*" Music Pictures Public snap Templates Videos ls --ignore="D*" Music Pictures Public snap Templates Videos ``` > 📌 Pay attention to option arguments when combining more single character options. 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