Environment variableAn environment variable is a user-definable value that can affect the way running processes will behave on a computer. Environment variables are part of the environment in which a process runs. For example, a running process can query the value of the TEMP environment variable to discover a suitable location to store temporary files, or the HOME or USERPROFILE variable to find the directory structure owned by the user running the process.PATH (variable)PATH is an environment variable on Unix-likeoperating systems, DOS, OS/2, and Microsoft Windows, specifying a set of directories where executable programs are located. In general, each executing process or user session has its own PATH setting. HistoryMultics originated the idea of a search path. The early Unix shell only looked for program names in /bin, but by Version 3 Unix the directory was too large and /usr/bin, and a search path, became part of the operating system.
Hidden file and hidden directoryIn computing, a hidden file or hidden directory is a file system object (such as a file or directory) that is excluded from a directory content report unless explicitly requested. The value of hiding files is generally to avoid showing the user files that are not likely to be of interest to them. The feature is not a security mechanism because access is not restricted; the user can request that normally-hidden files be displayed.
FilenameA filename is used to uniquely identify a computer file in a file system. Different file systems impose different restrictions on filename lengths.
Unix shellA Unix shell is a shell that provides a command-lineuser interface for a Unix-likeoperating system. A Unix shell provides a command language that can be used either interactively or for writing a shell script. A user typically works within a Unix shell via a terminal emulator; however, direct access via serial hardware connections or a Secure Shell are common for server systems.
C shellThe C shell (csh or the improved version, tcsh) is a Unix shell created by Bill Joy while he was a graduate student at University of California, Berkeley in the late 1970s. It has been widely distributed, beginning with the 2BSD release of the Berkeley Software Distribution (BSD) which Joy first distributed in 1978. Other early contributors to the ideas or the code were Michael Ubell, Eric Allman, Mike O'Brien and Jim Kulp.Command (computing)In computing, a command is a high-level instruction received via an external interface that directs the behavior of a computer program. Commonly, commands are sent to a program via a command-line interface, a script, a network protocol, or as an event triggered in a graphical user interface. Many commands support arguments to specify input and to modify default behavior. Terminology and syntax varies but there are notable common approaches.EvalIn some programming languages, eval, short for , is a function which evaluates a string as though it were an expression in the language, and returns a result; in others, it executes multiple lines of code as though they had been included instead of the line including the eval. The input to eval is not necessarily a string; it may be structured representation of code, such as an abstract syntax tree (like Lisp forms), or of special type such as code (as in Python).
Computer fileA computer file is a named collection of data treated as a unit by the system that manages it. Today, this system is called a file system. Many older computer systems lacked a distinct file system per se, yet a management feature is required in order to provide a file abstraction. Files can be shared with and transferred between computers and mobile devices via removable media, networks, or the Internet. Different types of computer files are designed for different purposes.Full stopThe full stop (Commonwealth English), period (North American English), or full point (.), is a punctuation mark used for several purposes, most often to mark the end of a declarative sentence (as distinguished from a question or exclamation). A full stop is frequently used at the end of word abbreviations—in British usage, primarily truncations such as Rev., but not after contractions which retain the final letter such as Revd; in American English, it is used in both cases.
Path (computing)A path (or filepath, file path, pathname, or similar) is a string that uniquely identifies an item in a hierarchical file system. Generally, a path is composed of directory names, special format specifiers, and optionally a filename, all separated by delimiters. This delimiter can vary by operating system, but popular, modern systems use the slash/, backslash\, or colon:.*As an Amazon Associate I earn from qualifying purchases.