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wait normally returns the exit status of the last job which terminated. It may also return 127 in the event that n specifies a non-existent job or zero if there were no jobs to wait for. Because wait needs to be aware of the job table of the current shell execution environment, it is usually implemented as a shell builtin .
Expect is an extension to the Tcl scripting language written by Don Libes. [2] The program automates interactions with programs that expose a text terminal interface. Expect, originally written in 1990 for the Unix platform, has since become available for Microsoft Windows and other systems.
Editing a FreeBSD shell script for configuring ipfirewall. 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 ...
The term "here document" or "here string" is also used for multiline string literals in various programming languages, notably Perl (syntax influenced by Unix shell), and languages influenced by Perl, notably PHP and Ruby. The shell-style << syntax is often retained, despite not being used for input redirection.
In computing, a shell is a computer program that exposes an operating system's services to a human user or other programs. In general, operating system shells use either a command-line interface (CLI) or graphical user interface (GUI), depending on a computer's role and particular operation.
The read function accepts an expression from the user, and parses it into a data structure in memory. For instance, the user may enter the s-expression (+ 1 2 3), which is parsed into a linked list containing four data elements. The eval function takes this internal data structure and evaluates it. In Lisp, evaluating an s-expression beginning ...
If a script is invoked as an argument to the interpreting shell, it will be executed regardless of whether the user holds the execute permission for that script. Although Windows also specifies an execute permission, none of the Windows-specific shells block script execution if the permission has not been granted.
This runs the ftp client with input user, press return, then pass. In casual use, the initial step of a pipeline is often cat or echo, reading from a file or string. This can often be replaced by input indirection or a here string, and use of cat and piping rather than input redirection is known as useless use of cat. For example, the following ...