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31 .\" @(#)printf.1 8.1 (Berkeley) 6/6/93
41 .Ar format Op Ar arguments ...
45 utility formats and prints its arguments, after the first, under control
50 is a character string which contains three types of objects: plain characters,
51 which are simply copied to standard output, character escape sequences which
52 are converted and copied to the standard output, and format specifications,
53 each of which causes printing of the next successive
58 after the first are treated as strings if the corresponding format is
63 otherwise it is evaluated as a C constant, with the following extensions:
65 .Bl -bullet -offset indent -compact
67 A leading plus or minus sign is allowed.
69 If the leading character is a single or double quote, the value is the
70 character code of the next character.
73 The format string is reused as often as necessary to satisfy the
75 Any extra format specifications are evaluated with zero or the null
78 Character escape sequences are in backslash notation as defined in the
81 The characters and their meanings
84 .Bl -tag -width Ds -offset indent -compact
86 Write a <bell> character.
88 Write a <backspace> character.
90 Write a <form-feed> character.
92 Write a <new-line> character.
94 Write a <carriage return> character.
96 Write a <tab> character.
98 Write a <vertical tab> character.
100 Write a <single quote> character.
102 Write a backslash character.
105 value is the 1-, 2-, or 3-digit
108 Multibyte characters can be constructed using multiple
113 Each format specification is introduced by the percent character
115 The remainder of the format specification includes,
116 in the following order:
118 .It "Zero or more of the following flags:"
122 specifying that the value should be printed in an ``alternate form''.
127 formats, this option has no effect.
130 formats the precision of the number is increased to force the first
131 character of the output string to a zero.
135 format, a non-zero result has the string
140 .Cm a , A , e , E , f , F , g
143 formats, the result will always contain a decimal point, even if no
144 digits follow the point (normally, a decimal point only appears in the
145 results of those formats if a digit follows the decimal point).
150 formats, trailing zeros are not removed from the result as they
153 A minus sign `\-' which specifies
155 of the output in the indicated field;
157 A `+' character specifying that there should always be
158 a sign placed before the number when using signed formats.
160 A space specifying that a blank should be left before a positive number
162 A `+' overrides a space if both are used;
164 A zero `0' character indicating that zero-padding should be used
165 rather than blank-padding.
166 A `\-' overrides a `0' if both are used;
169 An optional digit string specifying a
171 if the output string has fewer bytes than the field width it will
172 be blank-padded on the left (or right, if the left-adjustment indicator
173 has been given) to make up the field width (note that a leading zero
174 is a flag, but an embedded zero is part of a field width);
178 followed by an optional digit string giving a
180 which specifies the number of digits to appear after the decimal point,
185 formats, or the maximum number of bytes to be printed
186 from a string; if the digit string is missing, the precision is treated
189 A character which indicates the type of format to use (one of
190 .Cm diouxXfFeEgGaAcsb ) .
191 The uppercase formats differ from their lowercase counterparts only in
192 that the output of the former is entirely in uppercase.
193 The floating-point format specifiers
195 may be prefixed by an
197 to request that additional precision be used, if available.
200 A field width or precision may be
202 instead of a digit string.
205 supplies the field width or precision.
207 The format characters and their meanings are:
212 is printed as a signed decimal (d or i), unsigned octal, unsigned decimal,
213 or unsigned hexadecimal (X or x), respectively.
217 is printed in the style `[\-]ddd.ddd' where the number of d's
218 after the decimal point is equal to the precision specification for
220 If the precision is missing, 6 digits are given; if the precision
221 is explicitly 0, no digits and no decimal point are printed.
222 The values \*[If] and \*[Na] are printed as
230 is printed in the style
233 .Sq Op - Ar d.ddd No \(+- Ar dd
236 is one digit before the decimal point and the number after is equal to
237 the precision specification for the argument; when the precision is
238 missing, 6 digits are produced.
239 The values \*[If] and \*[Na] are printed as
253 whichever gives full precision in minimum space.
259 .Sq Op - Ar h.hhh No \(+- Li p Ar d
261 where there is one digit before the hexadecimal point and the number
262 after is equal to the precision specification for the argument;
263 when the precision is missing, enough digits are produced to convey
264 the argument's exact double-precision floating-point representation.
265 The values \*[If] and \*[Na] are printed as
275 Bytes from the string
277 are printed until the end is reached or until the number of bytes
278 indicated by the precision specification is reached; however if the
279 precision is 0 or missing, the string is printed entirely.
283 but interpret character escapes in backslash notation in the string
285 The permitted escape sequences are slightly different in that
290 and that an additional escape sequence
292 stops further output from this
296 Allows reordering of the output according to
299 Print a `%'; no argument is used.
303 character is defined in the program's locale (category
306 In no case does a non-existent or small field width cause truncation of
307 a field; padding takes place only if the specified field width exceeds
310 Some shells may provide a builtin
312 command which is similar or identical to this utility.
321 .Bd -literal -offset indent
322 $ printf "%s\en" hello
326 Same as above, but notice that the format string is not quoted and hence we
327 do not get the expected behavior:
328 .Bd -literal -offset indent
333 Print arguments forcing sign only for the first argument:
334 .Bd -literal -offset indent
335 $ printf "%+d\en%d\en%d\en" 1 -2 13
341 Same as above, but the single format string will be applied to the three
343 .Bd -literal -offset indent
344 $ printf "%+d\en" 1 -2 13
350 Print number using only two digits after the decimal point:
351 .Bd -literal -offset indent
352 $ printf "%.2f\en" 31.7456
358 behavior of converting arguments of numeric formats not beginning
359 with a digit to the ASCII
360 code of the first character is not supported.
369 command is expected to be compatible with the
378 after the standard library function,
381 ANSI hexadecimal character constants were deliberately not provided.
383 Trying to print a dash ("-") as the first character causes
385 to interpret the dash as a program argument.
390 If the locale contains multibyte characters
398 formats with a precision
399 may not operate as expected.
401 Since the floating point numbers are translated from ASCII
402 to floating-point and then back again, floating-point precision may be lost.
403 (By default, the number is translated to an IEEE-754 double-precision
404 value before being printed.
407 modifier may produce additional precision, depending on the hardware platform.)
409 The escape sequence \e000 is the string terminator.
410 When present in the argument for the
412 format, the argument will be truncated at the \e000 character.
414 Multibyte characters are not recognized in format strings (this is only
417 can appear inside a multibyte character).