4.3BSD-Tahoe/usr/man/cat3/printf.0
PRINTF(3S) UNIX Programmer's Manual PRINTF(3S)
NNAAMMEE
printf, fprintf, sprintf - formatted output conversion
SSYYNNOOPPSSIISS
##iinncclluuddee <<ssttddiioo..hh>>
pprriinnttff((ffoorrmmaatt [,, arg ] ... ))
cchhaarr **ffoorrmmaatt;;
ffpprriinnttff((ssttrreeaamm,, ffoorrmmaatt [,, arg ] ... ))
FFIILLEE **ssttrreeaamm;;
cchhaarr **ffoorrmmaatt;;
sspprriinnttff((ss,, ffoorrmmaatt [,, arg ] ... ))
cchhaarr **ss,, **ffoorrmmaatt;;
##iinncclluuddee <<vvaarraarrggss..hh>>
vvpprriinnttff((ffoorrmmaatt,, aarrggss))
cchhaarr **ffoorrmmaatt;;
vvaa__lliisstt aarrggss;;
vvffpprriinnttff((ssttrreeaamm,, ffoorrmmaatt,, aarrggss))
FFIILLEE **ssttrreeaamm;;
cchhaarr **ffoorrmmaatt;;
vvaa__lliisstt aarrggss;;
vvsspprriinnttff((ss,, ffoorrmmaatt,, aarrggss))
cchhaarr **ss,, **ffoorrmmaatt;;
vvaa__lliisstt aarrggss;;
DDEESSCCRRIIPPTTIIOONN
_P_r_i_n_t_f places output on the standard output stream ssttddoouutt.
_F_p_r_i_n_t_f places output on the named output _s_t_r_e_a_m. _S_p_r_i_n_t_f
places `output' in the string _s, followed by the character
`\0'. Alternate forms, in which the arguments have already
been captured using the variable-length argument facilities
of _v_a_r_a_r_g_s(3), are available under the names _v_p_r_i_n_t_f,
_v_f_p_r_i_n_t_f, and _v_s_p_r_i_n_t_f.
Each of these functions converts, formats, and prints its
arguments after the first under control of the first argu-
ment. The first argument is a character string which con-
tains two types of objects: plain characters, which are sim-
ply copied to the output stream, and conversion specifica-
tions, each of which causes conversion and printing of the
next successive _a_r_g _p_r_i_n_t_f.
Each conversion specification is introduced by the character
%%. The remainder of the conversion specification includes
in the following order
oo++ Zero or more of the following flags:
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PRINTF(3S) UNIX Programmer's Manual PRINTF(3S)
oo++ a `#' character specifying that the value should
be converted to an ``alternate form''. For cc, dd,
ss, and uu, conversions, this option has no effect.
For oo conversions, the precision of the number is
increased to force the first character of the out-
put string to a zero. For xx(XX) conversion, a
non-zero result has the string 00xx(00XX) prepended to
it. For ee, EE, ff, gg, and GG, conversions, 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 conver-
sions if a digit follows the decimal point). For
gg and GG conversions, trailing zeros are not
removed from the result as they would otherwise
be;
oo++ a minus sign `-' which specifies _l_e_f_t _a_d_j_u_s_t_m_e_n_t
of the converted value in the indicated field;
oo++ a `+' character specifying that there should
always be a sign placed before the number when
using signed conversions;
oo++ a space specifying that a blank should be left
before a positive number during a signed conver-
sion. A `+' overrides a space if both are used;
oo++ a zero `0' character indicating that zero-padding
should be used rather than blank-padding. A `-'
overrides a `0' if both are used;
oo++ an optional digit string specifying a _f_i_e_l_d _w_i_d_t_h; if
the converted value 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);
oo++ an optional period, followed by an optional digit
string giving a _p_r_e_c_i_s_i_o_n which specifies the number of
digits to appear after the decimal point, for e- and
f-conversion, or the maximum number of characters to be
printed from a string; if the digit string is missing,
the precision is treated as zero;
oo++ the character ll specifying that a following dd, ii, oo, xx,
or uu corresponds to a long integer _a_r_g, or that a fol-
lowing nn corresponds to a pointer to a long integer
_a_r_g;
oo++ the character hh specifying that a following dd, ii, oo, xx,
or uu corresponds to a short integer _a_r_g, or that a
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PRINTF(3S) UNIX Programmer's Manual PRINTF(3S)
following nn corresponds to a pointer to a short integer
_a_r_g;
oo++ a character which indicates the type of conversion to
be applied.
A field width or precision may be `*' instead of a digit
string. In this case an integer _a_r_g supplies the field
width or precision.
The conversion characters and their meanings are
ddooxx The integer _a_r_g is converted to signed decimal,
unsigned octal, or unsigned hexadecimal notation
respectively.
ii An alias for `d'.
ff The float or double _a_r_g is converted to decimal nota-
tion in the style `[--]ddd.ddd' where the number of d's
after the decimal point is equal to the precision
specification for the argument. If the precision is
missing, 6 digits are given; if the precision is expli-
citly 0, no digits and no decimal point are printed.
eeEE The float or double _a_r_g is converted in the style
`[--]d..dddee+_dd' where there is one digit before the
decimal point and the number after is equal to the pre-
cision specification for the argument; when the preci-
sion is missing, 6 digits are produced. An uppercase E
is used for `E' conversion.
ggGG The float or double _a_r_g is printed in style ff or in
style ee (EE) whichever gives full precision in minimum
space.
cc The character _a_r_g is printed.
ss _A_r_g is taken to be a string (character pointer) and
characters from the string are printed until a null
character or until the number of characters indicated
by the precision specification is reached; however if
the precision is 0 or missing all characters up to a
null are printed.
uu The unsigned integer _a_r_g is converted to decimal and
printed (the result will be in the range 0 through MAX-
UINT, where MAXUINT equals 4294967295 on a VAX-11 and
65535 on a PDP-11).
nn _A_r_g is taken to be a pointer to an integer (possibly
sshhoorrtt or lloonngg) through which is stored the number of
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PRINTF(3S) UNIX Programmer's Manual PRINTF(3S)
characters written to the output stream (or string) so
far by this call to pprriinnttff (or ffpprriinnttff, etc.).
pp _A_r_g is taken to be a pointer to vvooiidd; it is printed in
style xx.
%% Print a `%'; no argument is converted.
In no case does a non-existent or small field width cause
truncation of a field; padding takes place only if the
specified field width exceeds the actual width. Characters
generated by _p_r_i_n_t_f are printed as by _p_u_t_c(3S).
RREETTUURRNN VVAALLUUEE
The functions all return the number of characters printed,
or -1 if an error occurred.
EEXXAAMMPPLLEESS
To print a date and time in the form `Sunday, July 3,
10:02', where _w_e_e_k_d_a_y and _m_o_n_t_h are pointers to null-
terminated strings:
printf("%s, %s %d, %02d:%02d", weekday, month, day,
hour, min);
To print pi to 5 decimals:
printf("pi = %.5f", 4*atan(1.0));
SSEEEE AALLSSOO
putc(3S), scanf(3S)
BBUUGGSS
The functions still supports %_D, %_O, and %_U. Do not use
these formats, as they will be disappearing soon.
Printed 7/9/88 October 22, 1987 4