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In Unix and Unix-like operating systems, printf is a shell builtin (and utility program [2]) that formats and outputs text like the same-named C function. Originally named for outputting to a printer, it actually outputs to standard output. [3] The command accepts a format string, which specifies how to format values, and a list of values.
Command-line argument parsing is the process of analyzing and handling command-line input provided to a program.
The format string syntax and semantics is the same for all of the functions in the printf-like family. Mismatch between the format specifiers and count and type of values can cause a crash or vulnerability. The printf format string is complementary to the scanf format string, which provides formatted input (lexing a.k.a. parsing). Both format ...
In computing, Bash (short for "Bourne Again SHell,") [6] is an interactive command interpreter and command programming language developed for UNIX-like operating systems. [7] Created in 1989 [ 8 ] by Brian Fox for the GNU Project , it is supported by the Free Software Foundation and designed as a 100% free alternative for the Bourne shell ( sh ...
The test command in Unix evaluates the expression parameter. In most recent shell implementations, it is a shell builtin, even though the external version still exists.In the second form of the command, the [ ] (brackets) must be surrounded by blank spaces (this is because [is a program and POSIX compatible shells require a space between the program name and its arguments).
In Unix-like operating systems, true and false are commands whose only function is to always return with a predetermined exit status.Programmers and scripts often use the exit status of a command to assess success (exit status zero) or failure (non-zero) of the command.
Eval is understood to be the step of converting a quoted string into a callable function and its arguments, whereas apply is the actual call of the function with a given set of arguments. The distinction is particularly noticeable in functional languages , and languages based on lambda calculus , such as LISP and Scheme .
In computer programming, a usage message or help message is a brief message displayed by a program that utilizes a command-line interface for execution. This message usually consists of the correct command line usage for the program and includes a list of the correct command-line arguments or options acceptable to said program.