A Note on Search Paths

Search paths on this machine may need to include additional components drawn from the pod system. By way of example, the pod for GNU project software, /pod/gnu, may include /pod/gnu/bin, /pod/gnu/man, /pod/gnu/lib, and so forth. Provision has been made to generate complete paths from all pod components for command, libraries, manual pages, and include files.

Typically, such use will be included in the generic user environment configuration files. Run "pod" for further information.

Basic Unix Commands

NOTE: All commands must be in lowercase unless specified otherwise.

Click on the command for a more detailed explaination.

rsh/rlogin/rcp

These commands were used to login to remote machines within a given domain or within a given site, as well as for intermachine file copying and running remote commands. They are amazingly insecure and have allowed all local users to access any account including root for the last 15 years, as well as compromising all data sent through them. Any site still found to support these commands should be immediately overhauled for these and other serious security problems. Use ssh(1) and the related scp(1) commands instead.

cd dir_opt

The cd command is used the change directory, that is, it sets the current working directory of the current shell to be the directory specified after the cd. If no directory is specified, then the user's shell sets itself back to that user's home directory. If directory specifies a complete path starting with /, ., .., directory becomes the new working directory. If neither case applies, cd tries to find the designated directory relative to one of the paths specified by the $CDPATH shell variable. $CDPATH has the same syntax as, and similar semantics to, the $PATH shell variable. cd must have execute (search) permission in directory.

chgrp group files

Change the groupname on files to group for purposes of determining, on the filesystem objects so modified, which usergroup is referenced by the group modebits, as typically set by chmod. Use the -l option to ls to view file users and groups. Use the groups to list which groups you can apply.

chmod mode files

Change the permissions (or mode) on files either to a specific octal mode, or by a certain set of specific differences specified as a symbolic mode. Use the -l option to ls to view file modes.

chown user files

Change the owner of files to user for purposes of determining, on the filesystem objects so modified, which user is referenced by the user modebits, as typically set by chmod. Use the -l option to ls to view file owners and groups.

cp old new

The cp command is used to copy a file to a new location, or to copy many files into a target directory. Directory hierarchies can also be copied using the option -r.

To copy a file named image.jpg to the directory /vol/abyss/tmp with the new name of bleeding-heart.jpg the following command could be used:

cp image.jpg /vol/abyss/tmp/bleeding-heart.jpg

cp foo bar qux /vol/abyss/tmp

df -lk dir_opt

The df displays the amount of disk free on the filesystem containing each argument pathname. If no pathnames are given, the space available on all currently mounted filesystems is shown. The -k, --kilobytes switch prints sizes in 1K blocks instead of 512-byte blocks.

groups user_opt

Lists all groups of which you are (or a named user is) a member.

ls -FCas
ls -Flas

The ls command is used to list files in a directory, defaulting to the current directory. It is similar to the DOS command dir. There are many options available with ls, but the most commom have been prepacked at this site as l (that's just the letter "L" in lower case) for a short listing, and ll (that's two lowercase "L"s) for a long listing with file permissions, user and group ownerships, and last time of modification.

A specific list of files and/or directories may be given after the ls command or after one of its prepacked forms. A single dot can be used to refer to the current directory.

mkdir dirlist

The mkdir command is used to make directories. The specified directories are created, and are initially empty, meaning they only have entries . (dot) and .. (dotdot), which are names for the current and parent directories, respectively.

mv old new
mv files dir

The mv command is used to move file and/or directories to new locations. This includes simply moving a file to a new name within the current directory. This is very similar to the cp command except for several things:

1. The files will only be available via the new names/locations.
2. mv is usually much faster than cp.
3. They're spelled differently. :-)

please request

Please allows certain commands requiring root access to be run by a machine's primary users, as defined in the YP/NIS netgroup map. Running "please help" produces output like the following, depending on which subcommands have been locally provided:

	where request is one of the following single words,
	from the implemented functions marked with '*':
		* help      - output help about this program
		* allowed   - tell you if you may issue requests
		* reboot    - reboot this host
		* shutdown  - shutdown this host
		* halt      - shutdown this host
		* gamma     - modify the gamma level
		* automount - restart the automounter
		  renice    - make a process defer to others
		  kill      - kill a process
		  suspend   - suspend a process temporarily
		* tidydisk  - free up likely disk space
		* tablet    - configure a tablet for Alias
	Example: please help
	The executing user must have permission for the requested action.
	Most actions are automatically logged in the system logs.

ps options

ps prints certain information about active processes. Without options, information is printed about processes associated with the controlling terminal.

rm files

The rm command is used to remove files. Simply give the filenames to remove after the rm. Files thus removed are GONE FOREVER. The packaged version of rm here is nicer, and asks you, once, if you're sure you want to remove the files. However, if you say yes, they're still GONE FOREVER...

rmdir dirlist

The rmdir command is used to remove directories. The directories to remove must be empty at the time.

ssh hostname cmd_opt

Ssh connects to the specified hostname, and executes the specified cmd, or starts a login session in the absence of a command. Ssh copies its standard input to the remote command, the standard output of the remote command to its standard output, and the standard error of the remote command to its standard error. Ssh is very secure and allows a broad range of functionality, and is a complete replacement for rsh, rlogin, and rcp. Some initial setup is generally required unless rsh(1)-backward compatability is enabled by the system administrator.; see ssh-keygen(1) in the online manual for more information. It can also be used in combination with CVS using the CVS_RSH environment variable.

top

This command displays a sorted list of processes which are using some portion of the available CPU cycles on a machine. The display is updated every interval. The following fields are displayed in order for each process: user name, process ID, process group ID, CPU usage, processor currently executing the process ( if process not currently running), process priority, process size (in pages), resident set size (in pages), amount of CPU time used by the process, and the process name.

umask mask

The usermask, or umask, affects file access rights for certain classes of users through a system of default access denial. Note these these restrictions are modifications to base permissions of 666 for files (read/write access for everybody) and 777 for directories (list/modify/enter access for everybody).