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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.\" 4. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)printf.1 8.1 (Berkeley) 6/6/93 32.\" $FreeBSD$ 33.\" 34.Dd May 28, 2011 35.Dt PRINTF 1 36.Os 37.Sh NAME 38.Nm printf 39.Nd formatted output 40.Sh SYNOPSIS 41.Nm 42.Ar format Op Ar arguments ... 43.Sh DESCRIPTION 44The 45.Nm 46utility formats and prints its arguments, after the first, under control 47of the 48.Ar format . 49The 50.Ar format 51is a character string which contains three types of objects: plain characters, 52which are simply copied to standard output, character escape sequences which 53are converted and copied to the standard output, and format specifications, 54each of which causes printing of the next successive 55.Ar argument . 56.Pp 57The 58.Ar arguments 59after the first are treated as strings if the corresponding format is 60either 61.Cm c , b 62or 63.Cm s ; 64otherwise it is evaluated as a C constant, with the following extensions: 65.Pp 66.Bl -bullet -offset indent -compact 67.It 68A leading plus or minus sign is allowed. 69.It 70If the leading character is a single or double quote, the value is the 71character code of the next character. 72.El 73.Pp 74The format string is reused as often as necessary to satisfy the 75.Ar arguments . 76Any extra format specifications are evaluated with zero or the null 77string. 78.Pp 79Character escape sequences are in backslash notation as defined in the 80.St -ansiC , 81with extensions. 82The characters and their meanings 83are as follows: 84.Pp 85.Bl -tag -width Ds -offset indent -compact 86.It Cm \ea 87Write a <bell> character. 88.It Cm \eb 89Write a <backspace> character. 90.It Cm \ec 91Ignore remaining characters in this string. 92.It Cm \ef 93Write a <form-feed> character. 94.It Cm \en 95Write a <new-line> character. 96.It Cm \er 97Write a <carriage return> character. 98.It Cm \et 99Write a <tab> character. 100.It Cm \ev 101Write a <vertical tab> character. 102.It Cm \e\' 103Write a <single quote> character. 104.It Cm \e\e 105Write a backslash character. 106.It Cm \e Ns Ar num 107Write a byte whose 108value is the 1-, 2-, or 3-digit 109octal number 110.Ar num . 111Multibyte characters can be constructed using multiple 112.Cm \e Ns Ar num 113sequences. 114.El 115.Pp 116Each format specification is introduced by the percent character 117(``%''). 118The remainder of the format specification includes, 119in the following order: 120.Bl -tag -width Ds 121.It "Zero or more of the following flags:" 122.Bl -tag -width Ds 123.It Cm # 124A `#' character 125specifying that the value should be printed in an ``alternate form''. 126For 127.Cm b , c , d , s 128and 129.Cm u 130formats, this option has no effect. 131For the 132.Cm o 133formats the precision of the number is increased to force the first 134character of the output string to a zero. 135For the 136.Cm x 137.Pq Cm X 138format, a non-zero result has the string 139.Li 0x 140.Pq Li 0X 141prepended to it. 142For 143.Cm a , A , e , E , f , F , g 144and 145.Cm G 146formats, the result will always contain a decimal point, even if no 147digits follow the point (normally, a decimal point only appears in the 148results of those formats if a digit follows the decimal point). 149For 150.Cm g 151and 152.Cm G 153formats, trailing zeros are not removed from the result as they 154would otherwise be; 155.It Cm \&\- 156A minus sign `\-' which specifies 157.Em left adjustment 158of the output in the indicated field; 159.It Cm \&+ 160A `+' character specifying that there should always be 161a sign placed before the number when using signed formats. 162.It Sq \&\ \& 163A space specifying that a blank should be left before a positive number 164for a signed format. 165A `+' overrides a space if both are used; 166.It Cm \&0 167A zero `0' character indicating that zero-padding should be used 168rather than blank-padding. 169A `\-' overrides a `0' if both are used; 170.El 171.It "Field Width:" 172An optional digit string specifying a 173.Em field width ; 174if the output string has fewer bytes than the field width it will 175be blank-padded on the left (or right, if the left-adjustment indicator 176has been given) to make up the field width (note that a leading zero 177is a flag, but an embedded zero is part of a field width); 178.It Precision: 179An optional period, 180.Sq Cm \&.\& , 181followed by an optional digit string giving a 182.Em precision 183which specifies the number of digits to appear after the decimal point, 184for 185.Cm e 186and 187.Cm f 188formats, or the maximum number of bytes to be printed 189from a string; if the digit string is missing, the precision is treated 190as zero; 191.It Format: 192A character which indicates the type of format to use (one of 193.Cm diouxXfFeEgGaAcsb ) . 194The uppercase formats differ from their lowercase counterparts only in 195that the output of the former is entirely in uppercase. 196The floating-point format specifiers 197.Pq Cm fFeEgGaA 198may be prefixed by an 199.Cm L 200to request that additional precision be used, if available. 201.El 202.Pp 203A field width or precision may be 204.Sq Cm \&* 205instead of a digit string. 206In this case an 207.Ar argument 208supplies the field width or precision. 209.Pp 210The format characters and their meanings are: 211.Bl -tag -width Fl 212.It Cm diouXx 213The 214.Ar argument 215is printed as a signed decimal (d or i), unsigned octal, unsigned decimal, 216or unsigned hexadecimal (X or x), respectively. 217.It Cm fF 218The 219.Ar argument 220is printed in the style `[\-]ddd.ddd' where the number of d's 221after the decimal point is equal to the precision specification for 222the argument. 223If the precision is missing, 6 digits are given; if the precision 224is explicitly 0, no digits and no decimal point are printed. 225The values \*[If] and \*[Na] are printed as 226.Ql inf 227and 228.Ql nan , 229respectively. 230.It Cm eE 231The 232.Ar argument 233is printed in the style 234.Cm e 235.Sm off 236.Sq Op - Ar d.ddd No \(+- Ar dd 237.Sm on 238where there 239is one digit before the decimal point and the number after is equal to 240the precision specification for the argument; when the precision is 241missing, 6 digits are produced. 242The values \*[If] and \*[Na] are printed as 243.Ql inf 244and 245.Ql nan , 246respectively. 247.It Cm gG 248The 249.Ar argument 250is printed in style 251.Cm f 252.Pq Cm F 253or in style 254.Cm e 255.Pq Cm E 256whichever gives full precision in minimum space. 257.It Cm aA 258The 259.Ar argument 260is printed in style 261.Sm off 262.Sq Op - Ar h.hhh No \(+- Li p Ar d 263.Sm on 264where there is one digit before the hexadecimal point and the number 265after is equal to the precision specification for the argument; 266when the precision is missing, enough digits are produced to convey 267the argument's exact double-precision floating-point representation. 268The values \*[If] and \*[Na] are printed as 269.Ql inf 270and 271.Ql nan , 272respectively. 273.It Cm c 274The first byte of 275.Ar argument 276is printed. 277.It Cm s 278Bytes from the string 279.Ar argument 280are printed until the end is reached or until the number of bytes 281indicated by the precision specification is reached; however if the 282precision is 0 or missing, the string is printed entirely. 283.It Cm b 284As for 285.Cm s , 286but interpret character escapes in backslash notation in the string 287.Ar argument . 288The permitted escape sequences are slightly different in that 289octal escapes are 290.Cm \e0 Ns Ar num 291instead of 292.Cm \e Ns Ar num . 293.It Cm \&% 294Print a `%'; no argument is used. 295.El 296.Pp 297The decimal point 298character is defined in the program's locale (category 299.Dv LC_NUMERIC ) . 300.Pp 301In no case does a non-existent or small field width cause truncation of 302a field; padding takes place only if the specified field width exceeds 303the actual width. 304.Pp 305Some shells may provide a builtin 306.Nm 307command which is similar or identical to this utility. 308Consult the 309.Xr builtin 1 310manual page. 311.Sh EXIT STATUS 312.Ex -std 313.Sh COMPATIBILITY 314The traditional 315.Bx 316behavior of converting arguments of numeric formats not beginning 317with a digit to the 318.Tn ASCII 319code of the first character is not supported. 320.Sh SEE ALSO 321.Xr builtin 1 , 322.Xr echo 1 , 323.Xr sh 1 , 324.Xr printf 3 325.Sh STANDARDS 326The 327.Nm 328command is expected to be compatible with the 329.St -p1003.2 330specification. 331.Sh HISTORY 332The 333.Nm 334command appeared in 335.Bx 4.3 Reno . 336It is modeled 337after the standard library function, 338.Xr printf 3 . 339.Sh CAVEATS 340.Tn ANSI 341hexadecimal character constants were deliberately not provided. 342.Pp 343Trying to print a dash ("-") as the first character causes 344.Nm 345to interpret the dash as a program argument. 346.Nm -- 347must be used before 348.Ar format . 349.Pp 350If the locale contains multibyte characters 351(such as UTF-8), 352the 353.Cm c 354format and 355.Cm b 356and 357.Cm s 358formats with a precision 359may not operate as expected. 360.Sh BUGS 361Since the floating point numbers are translated from 362.Tn ASCII 363to floating-point and 364then back again, floating-point precision may be lost. 365(By default, the number is translated to an IEEE-754 double-precision 366value before being printed. 367The 368.Cm L 369modifier may produce additional precision, depending on the hardware platform.) 370.Pp 371The escape sequence \e000 is the string terminator. 372When present in the argument for the 373.Cm b 374format, the argument will be truncated at the \e000 character. 375.Pp 376Multibyte characters are not recognized in format strings (this is only 377a problem if 378.Ql % 379can appear inside a multibyte character).