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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.
These functions accept a format string parameter and a variable number of value parameters that the function serializes per the format string and writes to an output stream or a string buffer. The format string is encoded as a template language consisting of verbatim text and format specifiers that each specify how to serialize a value.
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.
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 ...
For function that manipulate strings, modern object-oriented languages, like C# and Java have immutable strings and return a copy (in newly allocated dynamic memory), while others, like C manipulate the original string unless the programmer copies data to a new string.
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).
These commands can be found on Unix operating systems and most Unix-like operating systems. This is not a comprehensive list of all utilities that existed in the various historic Unix and Unix-like systems, as it excludes utilities that were not mandated by the aforementioned standard.
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 .