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Since version 2.05b Bash can redirect standard input (stdin) from a "here string" using the <<< operator. Bash 3.0 supports in-process regular expression matching using a syntax reminiscent of Perl. [89] In February 2009, [90] Bash 4.0 introduced support for associative arrays. [4] Associative array indices are strings, in a manner similar to ...
This is a list of POSIX (Portable Operating System Interface) commands as specified by IEEE Std 1003.1-2024, which is part of the Single UNIX Specification (SUS). These commands can be found on Unix operating systems and most Unix-like operating systems.
In this way, a series of commands can be "piped" together, giving users the ability to quickly perform complex multi-stage processing from the command line or as part of a Unix shell script ("bash file"). In most Unix shells (command interpreters), this is represented by the vertical bar character. For example:
A metacharacter is a character that has a special meaning to a computer program, such as a shell interpreter or a regular expression (regex) engine.. In POSIX extended regular expressions, there are 14 metacharacters that must be escaped — preceded by a backslash (\) — in order to drop their special meaning and be treated literally inside an expression: opening and closing square brackets ...
The detailed semantics of "the" ternary operator as well as its syntax differs significantly from language to language. A top level distinction from one language to another is whether the expressions permit side effects (as in most procedural languages) and whether the language provides short-circuit evaluation semantics, whereby only the selected expression is evaluated (most standard ...
Bash, zsh and fish offer parameter name completion through a definition external to the command, distributed in a separate completion definition file. For command parameter name/value completions, these shells assume path/filename completion if no completion is defined for the command.
In logic, a set of symbols is commonly used to express logical representation. The following table lists many common symbols, together with their name, how they should be read out loud, and the related field of mathematics.
Kernel support for interpreter directives spread to other versions of Unix, and one modern implementation can be seen in the Linux kernel source in fs/binfmt_script.c. [31] This mechanism allows scripts to be used in virtually any context normal compiled programs can be, including as full system programs, and even as interpreters of other scripts.