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Process substitution can also be used to capture output that would normally go to a file, and redirect it to the input of a process. 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:
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 C shell can also read commands from a file, called a script. Like all Unix shells, it supports filename wildcarding, piping, here documents, command substitution, variables and control structures for condition-testing and iteration. What differentiated the C shell from others, especially in the 1980s, were its interactive features and ...
He "felt that commands should be usable as building blocks for writing more commands, just like subroutine libraries." [14] "There was a facility that would execute a bunch of commands stored in a file; it was called runcom for "run commands", and the file began to be called "a runcom". rc in Unix is a fossil from that usage." [15] [16] per RUNCOM:
A modern zsh installation comes with completion definitions for over five hundred commands. Tcsh offers default file, command, and variable name completion activated using Tab ↹. The 'complete' builtin command provides fully programmable completion. The source code comes with a 'complete.tcsh' file containing many examples of its completion ...
dd is a command-line utility for Unix, Plan 9, Inferno, and Unix-like operating systems and beyond, the primary purpose of which is to convert and copy files. [1] On Unix, device drivers for hardware (such as hard disk drives) and special device files (such as /dev/zero and /dev/random) appear in the file system just like normal files; dd can also read and/or write from/to these files ...
The most notable example is the cd command, which changes the working directory of the shell. Since each executable program runs in a separate process , and working directories are specific to each process, loading cd as an external program would not affect the working directory of the shell that loaded it.
The Single UNIX Specification (SUS) specifies that a series of tests are performed on the file specified on the command line: if the file cannot be read, or its Unix file type is undetermined, the file program will indicate that the file was processed but its type was undetermined. file must be able to determine the types directory, FIFO ...