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printf (Unix)
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<p>printf is a <a href="/facts/Shell_(computing)/Sa67elS7">shell</a> <a href="/facts/Command_(computing)/zUrvQbFy">command</a> that formats and outputs text like the <a href="/facts/Printf/Sc6Czbp2">same-named C function</a>. It is available in a variety of <a href="/facts/Unix/0pNL2seI">Unix</a> and <a href="/facts/Unix-like/YAKrAxzd">Unix-like</a> systems. Some shells implement the command as <a href="/facts/Shell_builtin/9o8PrWpa">builtin</a> and some systems provide it as a <a href="/facts/Software_utility/Hn3XtISQ">utility</a> <a href="/facts/Computer_program/e38jH9N9">program</a> </p><p>The command has similar <a href="/facts/Syntax_(programming_languages)/zM5oInza">syntax</a> and <a href="/facts/Semantics_(computer_science)/JEP1zyBv">semantics</a> as the library function. The command outputs text to <a href="/facts/Standard_output/r92M7Wd4">standard output</a> as specified by a format string and a list of values. <a href="/facts/Character_(computing)/X2zKLFFB">Characters</a> of the format string are copied to the output verbatim except when a format specifier is found which causes a value to be output per the specifier. </p><p>The command has some aspects unlike the library function. In addition to the library function format specifiers, %b causes the command to expand backslash <a href="/facts/Escape_sequence/r7lISrrw">escape sequences</a> (for example \n for <a href="/facts/Newline/ffeJz4Nn">newline</a>), and %q outputs an item that can be used as <a href="/facts/Shell_(computing)/Sa67elS7">shell</a> input. The value used for an unmatched specifier (too few values) is an empty string for %s or 0 for a numeric specifier. If there are more values than specifiers, then the command restarts processing the format string from its beginning, </p><p>The command is part of the <a href="/facts/X%2fOpen/btwVKbX2">X/Open</a> Portability Guide since issue 4 of 1992. It was inherited into the first version of POSIX.1 and the <a href="/facts/Single_Unix_Specification/w1ba5bDt">Single Unix Specification</a>. It first appeared in <a href="/facts/Berkeley_Software_Distribution/XQKcURrh">4.3BSD-Reno</a>. </p><p>The implementation bundled in <a href="/facts/GNU_Core_Utilities/Q9cop5U5">GNU Core Utilities</a> was written by David MacKenzie. It has an extension %q for escaping strings in POSIX-shell format. </p>