Term Description
tty Shorthand term for terminall and also a command on Unix and Unix-like operating systems to print the file name of the terminal connected to standard input. tty stands for TeleTYpewriter.
UNIX Spelled either UNIX or Unix and is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, development starting in the 1970s at the Bell Labs research center.
GNU Recursive acronym which stands for: GNU's Not Unix
BSD The Berkeley Software Distribution (BSD) was an operating system based on Research Unix. Today, "BSD" often refers to its descendants, such as FreeBSD, OpenBSD, NetBSD, or DragonFly BSD, and systems based on those descendants.
FreeBSD FreeBSD has similarities with Linux, with two major differences in scope and licensing: FreeBSD maintains a complete system, i.e. the project delivers a kernel, device drivers, userland utilities, and documentation, as opposed to Linux only delivering a kernel and drivers, and relying on third-parties for system software; and FreeBSD source code is generally released under a permissive BSD license, as opposed to the copyleft GPL used by Linux.
OpenBSD OpenBSD is a security-focused, free and open-source, Unix-like operating system based on the Berkeley Software Distribution (BSD).
NetBSD The NetBSD project focuses on code clarity, careful design, and portability across many computer architectures.
Absolute pathname A pathname that begins at the root directory., i.e. /
alias A name in place of a command. Alias' can be defined in for example ~/.bashrc
apropos A command that displays the reference page names and summary lines that contain a specified word or string of characters. The apropos command is the same as the man -k command.
builtin A command that is built into a shell, as opposed to a command from a seperate executable.
cron A daemon that executes commands at specified times and dates, according to instructions in the crontab file.
crontab file A file that specifies the dates and times at which e.g. user-specified commands are to be executed.
daemon A computer program that runs as a background process not under direct influence of a user.
emacs A text editor.
vim A text editor.
vi A text editor.
nano A text editor.
environement variable A variable used by the shell or commands run inside the shell. Such variable is available to all processes in the given process group. Further they are propagated by the creation of child processes, e.g. in a subshell.
EOF End-of-file. A condition where no data is left to be read from a data source.
Escape sequence A character (in the case of an 'escape' or character sequence used to protect a character from interpretation by a program. Usually an ASCII character, often backslash.
ex (editor)
field seperator
file descriptor
filename expansion
hard link
soft link
input redirection
job control
job number
parent directory
parent process
pid, PID Process ID - a unique number assigned to a process that is running.
POSIX A collection of standards proposed by the POSIX working groups of the Institute of Electrical and Electronics Engineers (IEEE).
pwd A command for displaying the absolute path of the current working directory
raw socket
regular expression Also called RegEx.
relative pathname A pathname that begins at a user's working directory
restricted shell A security feature which provide restricted shell access (limited features in a controlled environment)
root The loginname of the superuser (sysadmin), or the topmost directory, i.e. the first / in any absolute pathname.
sed sed is a powerful streamline editor for textfiles. It influenced later programs like AWK and Perl and was one of the first tools to support regular expressions. Released in 1974.
stdout standard output
stdin standard input
stderr standard error
termcap database
terminfo database
tilde substitution ~ is substituted with $HOME, i.e. your home directory. If your username is james231 the command vim ~/.bashrc will be turn into vim /home/james231/.bashrc
UID User ID. Also written as: uid.
variable expansion
wildcard character A placeholder such as *, +, ?, # which is interpreted differently. # is used as a wildcard character for digits, ? is used as a wildcard for 0-1 symbols, e.g. do? will match doc, do, doh, dos etc. do* will likewise match domination, do, dorm, dolomite and so on.
X Window System A windowing system for Unix-like operating systems. Currently at version 11 (i.e. X11) and has been since 1987. The X.Org foundation leads the X project.
X11 X is a windowing system that provides a basic framework for user interfaces. X11 refers to X version 11.