1.\" Copyright (c) 1989, 1990, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the Institute of Electrical and Electronics Engineers, Inc. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)printf.1 8.1 (Berkeley) 6/6/93 36.\" $FreeBSD$ 37.\" 38.Dd April 14, 2005 39.Dt PRINTF 1 40.Os 41.Sh NAME 42.Nm printf 43.Nd formatted output 44.Sh SYNOPSIS 45.Nm 46.Ar format Op Ar arguments ... 47.Sh DESCRIPTION 48The 49.Nm 50utility formats and prints its arguments, after the first, under control 51of the 52.Ar format . 53The 54.Ar format 55is a character string which contains three types of objects: plain characters, 56which are simply copied to standard output, character escape sequences which 57are converted and copied to the standard output, and format specifications, 58each of which causes printing of the next successive 59.Ar argument . 60.Pp 61The 62.Ar arguments 63after the first are treated as strings if the corresponding format is 64either 65.Cm c , b 66or 67.Cm s ; 68otherwise it is evaluated as a C constant, with the following extensions: 69.Pp 70.Bl -bullet -offset indent -compact 71.It 72A leading plus or minus sign is allowed. 73.It 74If the leading character is a single or double quote, the value is the 75.Tn ASCII 76code of the next character. 77.El 78.Pp 79The format string is reused as often as necessary to satisfy the 80.Ar arguments . 81Any extra format specifications are evaluated with zero or the null 82string. 83.Pp 84Character escape sequences are in backslash notation as defined in the 85.St -ansiC , 86with extensions. 87The characters and their meanings 88are as follows: 89.Pp 90.Bl -tag -width Ds -offset indent -compact 91.It Cm \ea 92Write a <bell> character. 93.It Cm \eb 94Write a <backspace> character. 95.It Cm \ec 96Ignore remaining characters in this string. 97.It Cm \ef 98Write a <form-feed> character. 99.It Cm \en 100Write a <new-line> character. 101.It Cm \er 102Write a <carriage return> character. 103.It Cm \et 104Write a <tab> character. 105.It Cm \ev 106Write a <vertical tab> character. 107.It Cm \e\' 108Write a <single quote> character. 109.It Cm \e\e 110Write a backslash character. 111.It Cm \e Ns Ar num 112.It Cm \e0 Ns Ar num 113Write an 8-bit character whose 114.Tn ASCII 115value is the 1-, 2-, or 3-digit 116octal number 117.Ar num . 118.El 119.Pp 120Each format specification is introduced by the percent character 121(``%''). 122The remainder of the format specification includes, 123in the following order: 124.Bl -tag -width Ds 125.It "Zero or more of the following flags:" 126.Bl -tag -width Ds 127.It Cm # 128A `#' character 129specifying that the value should be printed in an ``alternate form''. 130For 131.Cm c , d , 132and 133.Cm s , 134formats, this option has no effect. 135For the 136.Cm o 137formats the precision of the number is increased to force the first 138character of the output string to a zero. 139For the 140.Cm x 141.Pq Cm X 142format, a non-zero result has the string 143.Li 0x 144.Pq Li 0X 145prepended to it. 146For 147.Cm e , E , f , g , 148and 149.Cm G , 150formats, the result will always contain a decimal point, even if no 151digits follow the point (normally, a decimal point only appears in the 152results of those formats if a digit follows the decimal point). 153For 154.Cm g 155and 156.Cm G 157formats, trailing zeros are not removed from the result as they 158would otherwise be; 159.It Cm \&\- 160A minus sign `\-' which specifies 161.Em left adjustment 162of the output in the indicated field; 163.It Cm \&+ 164A `+' character specifying that there should always be 165a sign placed before the number when using signed formats. 166.It Sq \&\ \& 167A space specifying that a blank should be left before a positive number 168for a signed format. 169A `+' overrides a space if both are used; 170.It Cm \&0 171A zero `0' character indicating that zero-padding should be used 172rather than blank-padding. 173A `\-' overrides a `0' if both are used; 174.El 175.It "Field Width:" 176An optional digit string specifying a 177.Em field width ; 178if the output string has fewer characters than the field width it will 179be blank-padded on the left (or right, if the left-adjustment indicator 180has been given) to make up the field width (note that a leading zero 181is a flag, but an embedded zero is part of a field width); 182.It Precision: 183An optional period, 184.Sq Cm \&.\& , 185followed by an optional digit string giving a 186.Em precision 187which specifies the number of digits to appear after the decimal point, 188for 189.Cm e 190and 191.Cm f 192formats, or the maximum number of characters to be printed 193from a string; if the digit string is missing, the precision is treated 194as zero; 195.It Format: 196A character which indicates the type of format to use (one of 197.Cm diouxXfFeEgGaAcsb ) . 198The uppercase formats differ from their lowercase counterparts only in 199that the output of the former is entirely in uppercase. 200The floating-point format specifiers 201.Pq Cm fFeEgGaA 202may be prefixed by an 203.Cm L 204to request that additional precision be used, if available. 205.El 206.Pp 207A field width or precision may be 208.Sq Cm \&* 209instead of a digit string. 210In this case an 211.Ar argument 212supplies the field width or precision. 213.Pp 214The format characters and their meanings are: 215.Bl -tag -width Fl 216.It Cm diouXx 217The 218.Ar argument 219is printed as a signed decimal (d or i), unsigned octal, unsigned decimal, 220or unsigned hexadecimal (X or x), respectively. 221.It Cm fF 222The 223.Ar argument 224is printed in the style `[\-]ddd.ddd' where the number of d's 225after the decimal point is equal to the precision specification for 226the argument. 227If the precision is missing, 6 digits are given; if the precision 228is explicitly 0, no digits and no decimal point are printed. 229The values \*[If] and \*[Na] are printed as 230.Ql inf 231and 232.Ql nan , 233respectively. 234.It Cm eE 235The 236.Ar argument 237is printed in the style 238.Cm e 239.Sm off 240.Sq Op - Ar d.ddd No \(+- Ar dd 241.Sm on 242where there 243is one digit before the decimal point and the number after is equal to 244the precision specification for the argument; when the precision is 245missing, 6 digits are produced. 246The values \*[If] and \*[Na] are printed as 247.Ql inf 248and 249.Ql nan , 250respectively. 251.It Cm gG 252The 253.Ar argument 254is printed in style 255.Cm f 256.Pq Cm F 257or in style 258.Cm e 259.Pq Cm E 260whichever gives full precision in minimum space. 261.It Cm aA 262The 263.Ar argument 264is printed in style 265.Sm off 266.Sq Op - Ar h.hhh No \(+- Li p Ar d 267.Sm on 268where there is one digit before the hexadecimal point and the number 269after is equal to the precision specification for the argument; 270when the precision is missing, enough digits are produced to convey 271the argument's exact double-precision floating-point representation. 272The values \*[If] and \*[Na] are printed as 273.Ql inf 274and 275.Ql nan , 276respectively. 277.It Cm c 278The first character of 279.Ar argument 280is printed. 281.It Cm s 282Characters from the string 283.Ar argument 284are printed until the end is reached or until the number of characters 285indicated by the precision specification is reached; however if the 286precision is 0 or missing, all characters in the string are printed. 287.It Cm b 288As for 289.Cm s , 290but interpret character escapes in backslash notation in the string 291.Ar argument . 292.It Cm \&% 293Print a `%'; no argument is used. 294.El 295.Pp 296The decimal point 297character is defined in the program's locale (category 298.Dv LC_NUMERIC ) . 299.Pp 300In no case does a non-existent or small field width cause truncation of 301a field; padding takes place only if the specified field width exceeds 302the actual width. 303.Sh EXIT STATUS 304.Ex -std 305.Sh COMPATIBILITY 306The traditional 307.Bx 308behavior of converting arguments of numeric formats not beginning 309with a digit to the 310.Tn ASCII 311code of the first character is not supported. 312.Sh SEE ALSO 313.Xr echo 1 , 314.Xr printf 3 315.Sh STANDARDS 316The 317.Nm 318command is expected to be compatible with the 319.St -p1003.2 320specification. 321.Sh HISTORY 322The 323.Nm 324command appeared in 325.Bx 4.3 Reno . 326It is modeled 327after the standard library function, 328.Xr printf 3 . 329.Sh BUGS 330Since the floating point numbers are translated from 331.Tn ASCII 332to floating-point and 333then back again, floating-point precision may be lost. 334(By default, the number is translated to an IEEE-754 double-precision 335value before being printed. 336The 337.Cm L 338modifier may produce additional precision, depending on the hardware platform.) 339.Pp 340.Tn ANSI 341hexadecimal character constants were deliberately not provided. 342.Pp 343The escape sequence \e000 is the string terminator. 344When present in the argument for the 345.Cm b 346format, the argument will be truncated at the \e000 character. 347.Pp 348Multibyte characters are not recognized in format strings (this is only 349a problem if 350.Ql % 351can appear inside a multibyte character). 352