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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 .
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 iteration. The header often declares an explicit loop counter or loop variable. This allows the body ...
The following example shows how command-line completion works in Bash. Other command line shells may perform slightly differently. First we type the first three letters of our command: fir Then we press Tab ↹ and because the only command in our system that starts with "fir" is "firefox", it will be completed to: firefox
Download QR code; Print/export Download as PDF; Printable version; In other projects ... until (!CONDITION) loop. Infinite loop – Known as the repeat forever ...
Prints a command to the terminal as Bash reads it. Bash reads constructs all at once, such as compound commands which include if-fi and case-esac blocks. If a set -v is included within a compound command, then "verbose" will be enabled the next time Bash reads code as input, ie, after the end of the currently executing construct. [101]
The Shellshock bug affects Bash, a program that various Unix-based systems use to execute command lines and command scripts. It is often installed as the system's default command-line interface. Analysis of the source code history of Bash shows the bug was introduced on 5 August 1989, and released in Bash version 1.03 on 1 September 1989. [14 ...
This makes part of the data structure into a ring, causing naive code to loop forever. While most infinite loops can be found by close inspection of the code, there is no general method to determine whether a given program will ever halt or will run forever; this is the undecidability of the halting problem. [8]
IBM OS/2 [9] Microsoft Windows [10] ReactOS [11] HP MPE/iX [12] KolibriOS [13] SymbOS; Unix and Unix-like operating systems; Many shells, including all Bourne-like (such as Bash [14] or zsh [15]) and Csh-like shells as well as COMMAND.COM and cmd.exe implement echo as a builtin command. The command is also available in the EFI shell. [16]