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In computer science, a for-loop or for loop is a control flow statement for specifying iteration. Specifically, a for-loop functions by running a section of code repeatedly until a certain condition has been satisfied. For-loops have two parts: a header and a body. The header defines the iteration and the body is the code executed once per ...
A shell script can provide a convenient variation of a system command where special environment settings, command options, or post-processing apply automatically, but in a way that allows the new script to still act as a fully normal Unix command. One example would be to create a version of ls, the command to list files, giving it a shorter ...
Bash can execute the vast majority of Bourne shell scripts without modification, with the exception of Bourne shell scripts stumbling into fringe syntax behavior interpreted differently in Bash or attempting to run a system command matching a newer Bash builtin, etc. Bash command syntax includes ideas drawn from the Korn Shell (ksh) and the C ...
The Bourne shell (sh) is a shell command-line interpreter for computer operating systems.It first appeared on Version 7 Unix, as its default shell. Unix-like systems continue to have /bin/sh—which will be the Bourne shell, or a symbolic link or hard link to a compatible shell—even when other shells are used by most users.
Wrapper scripts often use this command to run a program (either directly or through an interpreter or virtual machine) after setting environment variables or other configuration. By using exec, the resources used by the shell program do not need to stay in use after the program is started. [2] The exec command can also perform a redirection.
Bash, zsh, and fish have completion for all variable names. PowerShell has completions for environment variable names, shell variable names and — from within user-defined functions — parameter names. Command argument completion is the completion of a specific command's arguments.
Such pipemill may not perform as intended if the body of the loop includes commands, such as cat and ssh, that read from stdin: [12] on the loop's first iteration, such a program (let's call it the drain) will read the remaining output from command, and the loop will then terminate (with results depending on the specifics of the drain). There ...
In computing, command substitution is a facility that allows a command to be run and its output to be pasted back on the command line as arguments to another command. Command substitution first appeared in the Bourne shell , [ 1 ] introduced with Version 7 Unix in 1979, and has remained a characteristic of all later Unix shells .