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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 ...
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.
The Bash command-line completion system is very flexible and customizable, and is often packaged with functions that complete arguments and filenames for specific programs and tasks. Bash's syntax has many extensions lacking in the Bourne shell. Bash can perform integer calculations ("arithmetic evaluation") without spawning external processes.
Mounting a file containing a disk image on a directory requires two steps: association of the file with a loop device node, mounting of the loop device at a mount point directory; These two operations can be performed either using two separate commands, or through special flags to the mount command.
The "rc" suffix on some Unix configuration files (for example, ".vimrc"), is a remnant of the RUNCOM ancestry of Unix shells. [ 1 ] [ 4 ] The PWB shell or Mashey shell, sh , was an upward-compatible version of the Thompson shell, augmented by John Mashey and others and distributed with the Programmer's Workbench UNIX , circa 1975–1977.
Everything is a file – describes one of the defining features of Unix; pipelines act on "files" in the Unix sense; Anonymous pipe – a FIFO structure used for interprocess communication; GStreamer – a pipeline-based multimedia framework; CMS Pipelines; Iteratee; Named pipe – persistent pipes used for interprocess communication
Similar to shell loops, a variable is changed as the loop starting the tasks iterates, so that many values can get passed to the specified command or script. pexec is a free software utility, and part of the GNU Project. [1] It is available [2] under the terms of GPLv3, and is part of the current Debian stable release. [3]
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: