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Because the while loop checks the condition/expression before the block is executed, the control structure is often also known as a pre-test loop. Compare this with the do while loop, which tests the condition/expression after the loop has executed. For example, in the languages C, Java, C#, [2] Objective-C, and C++, (which use the same syntax ...
In the C programming language, Duff's device is a way of manually implementing loop unrolling by interleaving two syntactic constructs of C: the do-while loop and a switch statement. Its discovery is credited to Tom Duff in November 1983, when Duff was working for Lucasfilm and used it to speed up a real-time animation program.
This functions similarly to Bash's Ctrl+R history search, but is always on, giving the user continuous feedback while typing commands. Fish also includes feature-rich tab completion , with support for expanding file paths (with wildcards and brace expansion ), environment variables , and command-specific completions.
One example of this is Bash, which offers the same grammar and syntax as the Bourne shell, and which also provides a POSIX-compliant mode. [13] As such, most shell scripts written for the Bourne shell can be run in BASH, but the reverse may not be true since BASH has extensions which are not present in the Bourne shell.
Infinite loops can be implemented using various control flow constructs. Most commonly, in unstructured programming this is jump back up , while in structured programming this is an indefinite loop (while loop) set to never end, either by omitting the condition or explicitly setting it to true, as while (true) ....
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.
The example ~/.bash_profile below is compatible with the Bourne shell and gives semantics similar to csh for the ~/.bashrc and ~/.bash_login. The [ -r filename ] && cmd is a short-circuit evaluation that tests if filename exists and is readable, skipping the part after the && if it is not.
Other processes can use the CPU while the caller is blocked. The scheduler is given the information needed to implement priority inheritance or other mechanisms to avoid starvation. Busy-waiting itself can be made much less wasteful by using a delay function (e.g., sleep()) found in most operating systems. This puts a thread to sleep for a ...