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In the above example, the main( ) function defines where the program should start executing. The function body consists of a single statement, a call to the printf() function, which stands for "print formatted"; it outputs to the console whatever is passed to it as the parameter, in this case the string "hello, world".
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.
The term is also used more generally to mean the automated mode of running an operating system shell; each operating system uses a particular name for these functions including batch files (MSDos-Win95 stream, OS/2), command procedures (VMS), and shell scripts (Windows NT stream and third-party derivatives like 4NT—article is at cmd.exe), and ...
An example of the printf function. printf is a C standard library function that formats text and writes it to standard output. The name, printf is short for print formatted where print refers to output to a printer although the functions are not limited to printer output. The standard library provides many other similar functions that form a ...
printf(string format, items-to-format) It can take one or more arguments, where the first argument is a string to be written. This string can contain special formatting codes which are replaced by items from the remainder of the arguments. For example, an integer can be printed using the "%d" formatting code, e.g.: printf("%d", 42);
The printf function emulates the standard C printf and works similarly to the print command described above. The pattern to match, however, works as follows: NR is the number of records, typically lines of input, AWK has so far read, i.e. the current line number, starting at 1 for the first line of input.
The problem stems from the use of unchecked user input as the format string parameter in certain C functions that perform formatting, such as printf(). A malicious user may use the %s and %x format tokens, among others, to print data from the call stack or possibly other locations in memory.
The C programming language provides many standard library functions for file input and output.These functions make up the bulk of the C standard library header <stdio.h>. [1] The functionality descends from a "portable I/O package" written by Mike Lesk at Bell Labs in the early 1970s, [2] and officially became part of the Unix operating system in Version 7.