1.\" $NetBSD: printf.1,v 1.17 2002/11/24 22:35:45 christos Exp $ 2.\" 3.\" Copyright (c) 1989, 1990, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" the Institute of Electrical and Electronics Engineers, Inc. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the University of 20.\" California, Berkeley and its contributors. 21.\" 4. Neither the name of the University nor the names of its contributors 22.\" may be used to endorse or promote products derived from this software 23.\" without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35.\" SUCH DAMAGE. 36.\" 37.\" from: @(#)printf.1 8.1 (Berkeley) 6/6/93 38.\" 39.Dd November 5, 1993 40.Dt PRINTF 1 41.Os 42.Sh NAME 43.Nm printf 44.Nd formatted output 45.Sh SYNOPSIS 46.Nm 47.Ar format 48.Op Ar arguments ... 49.Sh DESCRIPTION 50.Nm 51formats and prints its arguments, after the first, under control 52of the 53.Ar format . 54The 55.Ar format 56is a character string which contains three types of objects: plain characters, 57which are simply copied to standard output, character escape sequences which 58are converted and copied to the standard output, and format specifications, 59each of which causes printing of the next successive 60.Ar argument . 61.Pp 62The 63.Ar arguments 64after the first are treated as strings if the corresponding format is 65either 66.Cm b , 67.Cm B , 68.Cm c 69or 70.Cm s ; 71otherwise it is evaluated as a C constant, with the following extensions: 72.Pp 73.Bl -bullet -offset indent -compact 74.It 75A leading plus or minus sign is allowed. 76.It 77If the leading character is a single or double quote, the value is the 78.Tn ASCII 79code of the next character. 80.El 81.Pp 82The format string is reused as often as necessary to satisfy the 83.Ar arguments . 84Any extra format specifications are evaluated with zero or the null 85string. 86.Pp 87Character escape sequences are in backslash notation as defined in 88.St -ansiC . 89The characters and their meanings are as follows: 90.Bl -tag -width Ds -offset indent 91.It Cm \ee 92Write an \*[Lt]escape\*[Gt] character. 93.It Cm \ea 94Write a \*[Lt]bell\*[Gt] character. 95.It Cm \eb 96Write a \*[Lt]backspace\*[Gt] character. 97.It Cm \ef 98Write a \*[Lt]form-feed\*[Gt] character. 99.It Cm \en 100Write a \*[Lt]new-line\*[Gt] character. 101.It Cm \er 102Write a \*[Lt]carriage return\*[Gt] character. 103.It Cm \et 104Write a \*[Lt]tab\*[Gt] character. 105.It Cm \ev 106Write a \*[Lt]vertical tab\*[Gt] character. 107.It Cm \e\' 108Write a \*[Lt]single quote\*[Gt] character. 109.It Cm \e" 110Write a \*[Lt]double quote\*[Gt] character. 111.It Cm \e\e 112Write a backslash character. 113.It Cm \e Ns Ar num 114Write an 8\-bit character whose 115.Tn ASCII 116value is the 1\-, 2\-, or 3\-digit octal number 117.Ar num . 118.It Cm \ex Ns Ar xx 119Write an 8\-bit character whose 120.Tn ASCII 121value is the 1\- or 2\-digit hexadecimal number 122.Ar xx . 123.El 124.Pp 125Each format specification is introduced by the percent character 126(``%''). 127The remainder of the format specification includes, 128in the following order: 129.Bl -tag -width Ds 130.It "Zero or more of the following flags:" 131.Bl -tag -width Ds 132.It Cm # 133A `#' character 134specifying that the value should be printed in an ``alternative form''. 135For 136.Cm b , 137.Cm c , 138.Cm d , 139and 140.Cm s 141formats, this option has no effect. 142For the 143.Cm o 144format the precision of the number is increased to force the first 145character of the output string to a zero. 146For the 147.Cm x 148.Pq Cm X 149format, a non-zero result has the string 150.Li 0x 151.Pq Li 0X 152prepended to it. 153For 154.Cm e , 155.Cm E , 156.Cm f , 157.Cm g , 158and 159.Cm G 160formats, the result will always contain a decimal point, even if no 161digits follow the point (normally, a decimal point only appears in the 162results of those formats if a digit follows the decimal point). 163For 164.Cm g 165and 166.Cm G 167formats, trailing zeros are not removed from the result as they 168would otherwise be. 169.\" I turned this off - decided it isn't a valid use of '#' 170.\" For the 171.\" .Cm B 172.\" format, backslash-escape sequences are expanded first; 173.It Cm \&\- 174A minus sign `\-' which specifies 175.Em left adjustment 176of the output in the indicated field; 177.It Cm \&+ 178A `+' character specifying that there should always be 179a sign placed before the number when using signed formats. 180.It Sq \&\ \& 181A space specifying that a blank should be left before a positive number 182for a signed format. 183A `+' overrides a space if both are used; 184.It Cm \&0 185A zero `0' character indicating that zero-padding should be used 186rather than blank-padding. 187A `\-' overrides a `0' if both are used; 188.El 189.It "Field Width:" 190An optional digit string specifying a 191.Em field width ; 192if the output string has fewer characters than the field width it will 193be blank-padded on the left (or right, if the left-adjustment indicator 194has been given) to make up the field width (note that a leading zero 195is a flag, but an embedded zero is part of a field width); 196.It Precision : 197An optional period, 198.Sq Cm \&.\& , 199followed by an optional digit string giving a 200.Em precision 201which specifies the number of digits to appear after the decimal point, 202for 203.Cm e 204and 205.Cm f 206formats, or the maximum number of characters to be printed 207from a string 208.Sm off 209.Pf ( Cm b No , 210.Sm on 211.Cm B 212and 213.Cm s 214formats); if the digit string is missing, the precision is treated 215as zero; 216.It Format : 217A character which indicates the type of format to use (one of 218.Cm diouxXfwEgGbBcs ) . 219.El 220.Pp 221A field width or precision may be 222.Sq Cm \&* 223instead of a digit string. 224In this case an 225.Ar argument 226supplies the field width or precision. 227.Pp 228The format characters and their meanings are: 229.Bl -tag -width Fl 230.It Cm diouXx 231The 232.Ar argument 233is printed as a signed decimal (d or i), unsigned octal, unsigned decimal, 234or unsigned hexadecimal (X or x), respectively. 235.It Cm f 236The 237.Ar argument 238is printed in the style 239.Sm off 240.Pf [\-]ddd Cm \&. No ddd 241.Sm on 242where the number of d's 243after the decimal point is equal to the precision specification for 244the argument. 245If the precision is missing, 6 digits are given; if the precision 246is explicitly 0, no digits and no decimal point are printed. 247.It Cm eE 248The 249.Ar argument 250is printed in the style 251.Sm off 252.Pf [\-]d Cm \&. No ddd Cm e No \\*(Pmdd 253.Sm on 254where there 255is one digit before the decimal point and the number after is equal to 256the precision specification for the argument; when the precision is 257missing, 6 digits are produced. 258An upper-case E is used for an `E' format. 259.It Cm gG 260The 261.Ar argument 262is printed in style 263.Cm f 264or in style 265.Cm e 266.Pq Cm E 267whichever gives full precision in minimum space. 268.It Cm b 269Characters from the string 270.Ar argument 271are printed with backslash-escape sequences expanded. 272.br 273The following additional backslash-escape sequences are supported: 274.Bl -tag -width Ds 275.It Cm \ec 276Causes 277.Nm 278to ignore any remaining characters in the string operand containing it, 279any remaining string operands, and any additional characters in 280the format operand. 281.It Cm \e0 Ns Ar num 282Write an 8\-bit character whose 283.Tn ASCII 284value is the 1\-, 2\-, or 3\-digit 285octal number 286.Ar num . 287.It Cm \e^ Ns Ar c 288Write the control character 289.Ar c . 290Generates characters `\e000' through `\e037`, and `\e177' (from `\e^?'). 291.It Cm \eM\- Ns Ar c 292Write the character 293.Ar c 294with the 8th bit set. 295Generates characters `\e241' through `\e376`. 296.It Cm \eM^ Ns Ar c 297Write the control character 298.Ar c 299with the 8th bit set. 300Generates characters `\e000' through `\e037`, and `\e177' (from `\eM^?'). 301.El 302.It Cm B 303Characters from the string 304.Ar argument 305are printed with unprintable characters backslash-escaped using the 306.Sm off 307.Pf ` Cm \e Ar c No ', 308.Pf ` Cm \e^ Ar c No ', 309.Pf ` Cm \eM\- Ar c No ' 310or 311.Pf ` Cm \eM^ Ar c No ', 312.Sm on 313formats described above. 314.It Cm c 315The first character of 316.Ar argument 317is printed. 318.It Cm s 319Characters from the string 320.Ar argument 321are printed until the end is reached or until the number of characters 322indicated by the precision specification is reached; if the 323precision is omitted, all characters in the string are printed. 324.It Cm \&% 325Print a `%'; no argument is used. 326.El 327.Pp 328In no case does a non-existent or small field width cause truncation of 329a field; padding takes place only if the specified field width exceeds 330the actual width. 331.Sh EXIT STATUS 332.Nm 333exits 0 on success, 1 on failure. 334.Sh SEE ALSO 335.Xr echo 1 , 336.Xr printf 3 , 337.Xr printf 9 338.Xr vis 3 339.Sh STANDARDS 340The 341.Nm 342utility conforms to 343.St -p1003.1-2001 . 344.Pp 345Support for the floating point formats and `*' as a field width and precision 346are optional in POSIX. 347.Pp 348The behaviour of the %B format and the \e', \e", \exxx, \ee and 349\e[M][\-|^]c escape sequences are undefined in POSIX. 350.Sh BUGS 351Since the floating point numbers are translated from 352.Tn ASCII 353to floating-point and 354then back again, floating-point precision may be lost. 355.Pp 356Hexadecimal character constants are restricted to, and should be specified 357as, two character constants. This is contrary to the ISO C standard but 358does guarantee detection of the end of the constant. 359