printf - formatted output


printf format [arguments  ...]


The printf(1) utility takes its first argument as a format, and uses that format for printing all remaining arguments. The format is a character string that contains three types of objects: plain characters, which are simply copied to standard output; character escape sequences, which are converted and copied to the standard output; and format specifications, each of which causes printing of the next successive argument.

The arguments after the first are treated as strings if the corresponding format is either c or s; otherwise it is evaluated as a C constant, with the following extensions:

The format string is reused as often as necessary to satisfy the arguments. Any extra format specifications are evaluated with zero or the null string.

Character escape sequences are in backslash (\) notation as defined in the ISO or ANSI C Standard. The characters and their meanings are as follows:

\a Write a <bell> character.
\b Write a <back-space> character.
\f Write a <form-feed> character.
\n Write a <newline> character.
\r Write a <carriage-return> character.
\t Write a <tab> character.
\v Write a <vertical-tab> character.
\' Write a <single-quote> character.
\\ Write a backslash character.
\ddd Write an eight-bit character whose ASCII value is the one-, two-, or three-digit octal number ddd.

Each format specification is introduced by the percent character (%).

The remainder of the format specification includes, in the following order, zero or more of the following flags:
Specifies that the value should be printed in an "alternate form." For c, d, and s, formats, this option has no effect. For the o formats the precision of the number is increased to force the first character of the output string to a zero. For the x (X) format, a non-zero result has the string 0x (0X) prepended to it. For e, E, f, g, and G, formats, the result will always contain a decimal point, even if no digits follow the point (normally, a decimal point only appears in the results of those formats if a digit follows the decimal point). For g and G formats, trailing zeros are not removed from the result as they would otherwise be.
Specifies left adjustment of the output in the indicated field.
Specifies that there should always be a sign placed before the number when using signed formats.
' '
A space; specifies that a blank should be left before a positive number for a signed format. A '+' overrides a space if both are used.
A zero; indicates that zero-padding should be used rather than blank-padding. A '-' overrides a '0' if both are used.
Field width
An optional digit string specifying a field width. If the output string has fewer characters than the field width, it will be blank-padded on the left (or right, if the left-adjustment indicator has been given) to make up the field width (note that a leading zero is a flag, but an embedded zero is part of a field width).
An optional period, '.', followed by an optional digit string giving a precision that specifies the number of digits to appear after the decimal point, for e and f formats, or the maximum number of characters to be printed from a string. If the digit string is missing, the precision is treated as zero.
A character that indicates the type of format to use (one of diouxXfwEgGcs).

A field width or precision can be '*' instead of a digit string. In this case, an argument supplies the field width or precision.

The format characters and their meanings are:

The argument is printed as a signed decimal (d or i), unsigned decimal, unsigned octal, or unsigned hexadecimal (X or x), respectively. The argument is printed in the style '[-]ddd.ddd' where the number of occurrences of d after the decimal point is equal to the precision specification for the argument. If the precision is missing, six digits are given; if the precision is explicitly 0, no digits and no decimal point are printed.
The argument is printed in the style e where there is one digit before the decimal point, and the number after is equal to the precision specification for the argument; when the precision is missing, six digits are produced. An uppercase E is used for an E format.
The argument is printed in style f or in style e (E), whichever gives full precision in minimum space.
The first character of argument is printed.
Characters from the string argument are printed until the end is reached, or until the number of characters indicated by the precision specification is reached. If the precision is 0 or missing, however, all characters in the string are printed.
Print a '%'; no argument is used.

In no case does a nonexistent or small field width cause truncation of a field. Padding takes place only if the specified field width exceeds the actual width.


The printf(1) utility exits 0 on success, 1 on failure.


Because the floating-point numbers are translated from ASCII to floating-point and then back again, floating-point precision might be lost.

ANSI hexadecimal character constants were deliberately not provided.