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The test command in Unix evaluates the expression parameter. In most recent shell implementations, it is a shell builtin, even though the external version still exists.In the second form of the command, the [ ] (brackets) must be surrounded by blank spaces (this is because [is a program and POSIX compatible shells require a space between the program name and its arguments).
A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. [1] The various dialects of shell scripts are considered to be command languages . Typical operations performed by shell scripts include file manipulation, program execution, and printing text.
In Unix-like operating systems, true and false are commands whose only function is to always return with a predetermined exit status.Programmers and scripts often use the exit status of a command to assess success (exit status zero) or failure (non-zero) of the command.
In computing, Bash (short for "Bourne Again SHell,") [6] is an interactive command interpreter and command programming language developed for UNIX-like operating systems. [7] Created in 1989 [ 8 ] by Brian Fox for the GNU Project , it is supported by the Free Software Foundation and designed as a 100% free alternative for the Bourne shell ( sh ...
A Unix shell is a command-line interpreter or shell that provides a command line user interface for Unix-like operating systems. The shell is both an interactive command language and a scripting language , and is used by the operating system to control the execution of the system using shell scripts .
Previously (and in fact still) the shell did much of this job; it automatically executed itself on a text file with executable mode when the text file's name was typed as a command. Putting the facility into the system gives the following benefits. 1) It makes shell scripts more like real executable files, because they can be the subject of 'exec.'
Version 1 AT&T UNIX comm: Text processing Mandatory Select or reject lines common to two files Version 4 AT&T UNIX command: Shell programming Mandatory Execute a simple command compress: Filesystem Optional (XSI) Compress data 4.3BSD cp: Filesystem Mandatory Copy files PDP-7 UNIX crontab: Misc Mandatory Schedule periodic background work System ...
The Unix system had been written almost exclusively in C, so the C shell's first objective was a command language that was more stylistically consistent with the rest of the system. The keywords, the use of parentheses, and the C shell's built-in expression grammar and support for arrays were all strongly influenced by C.