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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 ...
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 .
Interpreter directives allow scripts and data files to be used as commands, hiding the details of their implementation from users and other programs, by removing the need to prefix scripts with their interpreter on the command line. For example, consider a script having the initial line #!/bin/sh -x.
Python, Ruby, Lua, XLNT, and other interpreters also have command shells for interactive use. FreeBSD uses tcsh as its default interactive shell for the superuser, and ash as default scripting shell. Many Linux distributions have the Bash implementation of the Unix shell. Apple macOS and some Linux distributions use zsh.
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, Linux and other Unix-like operating systems, the first two bytes in a file can be the characters "#!", which constitute a magic number (hexadecimal 23 and 21, the ASCII values of "#" and "!") often referred to as shebang, prefix the first line in a script, with the remainder of the line being a command usually limited to a max of 14 ...
The Bash syntax for writing to a process is >(command). Here is an example using the tee , wc and gzip commands that counts the lines in a file with wc -l and compresses it with gzip in one pass:
A shell script (or job) can report progress of long running tasks to the interactive user. Unix/Linux systems may offer other tools support using progress indicators from scripts or as standalone-commands, such as the program "pv". [52] These are not integrated features of the shells, however.