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Retrieve text string from messages object with plural form nice: Process management Mandatory Invoke a utility with an altered nice value Version 4 AT&T UNIX nl: Text processing Optional (XSI) Line numbering filter System III nm: C programming Optional (SD, XSI) Write the name list of an object file: Version 1 AT&T UNIX nohup: Process ...
Multics also introduced the active function, a key concept in all later shells. This is defined as . a string... which is replaced by a character string return value before the command line containing it is executed. Active functions are often used... to implement command-language macros. [11]
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.
The Bash command-line completion system is very flexible and customizable, and is often packaged with functions that complete arguments and filenames for specific programs and tasks. Bash's syntax has many extensions lacking in the Bourne shell. Bash can perform integer calculations ("arithmetic evaluation") without spawning external processes.
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).
Some programming languages, such as C, C++ and Java, allow a program to interpret the command-line arguments by handling them as string parameters in the main function. [21] [22] Other languages, such as Python, expose operating system specific API (functionality) through sys module, and in particular sys.argv for command-line arguments.
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The term is also used more generally to mean the automated mode of running an operating system shell; each operating system uses a particular name for these functions including batch files (MSDos-Win95 stream, OS/2), command procedures (VMS), and shell scripts (Windows NT stream and third-party derivatives like 4NT—article is at cmd.exe), and ...