2.11BSD/man/cat1/printf.0
PRINTF(1) UNIX Programmer's Manual PRINTF(1)
NAME
printf - formatted output
SYNOPSIS
printf format [ arguments ... ]
DESCRIPTION
Printf formats and prints its arguments, after the first,
under control of the _f_o_r_m_a_t. The _f_o_r_m_a_t is a character
string which contains three types of objects: plain charac-
ters, which are simply copied to standard output, character
escape sequences which are converted and copied to the stan-
dard output, and format specifications, each of which causes
printing of the next successive _a_r_g_u_m_e_n_t.
The _a_r_g_u_m_e_n_t_s after the first are treated as strings if the
corresponding format is either c or s; otherwise it is
evaluated as a C constant, with the following extensions:
o+ A leading plus or minus sign is allowed.
o+ If the leading character is a single or double quote,
or not a digit, plus, or minus sign, the value is the
ASCII code of the next character.
The format string is reused as often as necessary to satisfy
the _a_r_g_u_m_e_n_t_s. Any extra format specifications are
evaluated with zero or the null string.
Character escape sequences are in backslash notation as
defined in the draft proposed ANSI C Standard X3J11. The
characters and their meanings are as follows:
\a Write a <bell> character.
\b Write a <backspace> character.
\f Write a <form-feed> character.
\n Write a <new-line> character.
\r Write a <carriage return> character.
\t Write a <tab> character.
\v Write a <vertical tab> character.
\' Write a <single quote> character.
\\ Write a backslash character.
\_n_u_m Write an 8-bit character whose ASCII value is the
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1-, 2-, or 3-digit octal number _n_u_m.
Each format specification is introduced by the percent char-
acter (``%''). The remainder of the format specification
includes, in the following order:
"Zero or more of the following flags:"
# A `#' character specifying that the value should
be printed in an ``alternate form''. For c, d,
and s, formats, this option has no effect. For
the o formats the precision of the number is
increased to force the first character of the out-
put string to a zero. For the x (X) format, a
non-zero result has the string 0x (0X) prepended
to it. For e, E, f, g, and G, formats, 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 formats if a
digit follows the decimal point). For g and G
formats, trailing zeros are not removed from the
result as they would otherwise be;
- A minus sign `-' which specifies _l_e_f_t _a_d_j_u_s_t_m_e_n_t
of the output in the indicated field;
+ A `+' character specifying that there should
always be a sign placed before the number when
using signed formats.
` ' A space specifying that a blank should be left
before a positive number for a signed format. A
`+' overrides a space if both are used;
0 A zero `0' character indicating that zero-padding
should be used rather than blank-padding. A `-'
overrides a `0' if both are used;
Field Width:
An optional digit string specifying a _f_i_e_l_d _w_i_d_t_h;
if the output string 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);
Precision:
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
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point, for e and f formats, or the maximum number
of characters to be printed from a string; if the
digit string is missing, the precision is treated
as zero;
Format:
A character which indicates the type of format to
use (one of diouxXfwEgGcs).
A field width or precision may be * instead of a digit
string. In this case an _a_r_g_u_m_e_n_t supplies the field width
or precision.
The format characters and their meanings are:
diouXx The _a_r_g_u_m_e_n_t is printed as a signed decimal (d or
i), unsigned decimal, unsigned octal, or unsigned
hexadecimal (X or x), respectively.
f The _a_r_g_u_m_e_n_t is printed in the style `[-]ddd.ddd'
where the number of d's after the decimal point is
equal to the precision specification for the argu-
ment. If the precision is missing, 6 digits are
given; if the precision is explicitly 0, no digits
and no decimal point are printed.
eE The _a_r_g_u_m_e_n_t is printed in the style e where there
is one digit before the decimal point and the
number after is equal to the precision specifica-
tion for the argument; when the precision is miss-
ing, 6 digits are produced. An upper-case E is
used for an `E' format.
gG The _a_r_g_u_m_e_n_t is printed in style f or in style e
(E) whichever gives full precision in minimum
space.
c The first character of _a_r_g_u_m_e_n_t is printed.
s Characters from the string _a_r_g_u_m_e_n_t are printed
until the end is reached or until the number of
characters indicated by the precision specifica-
tion is reached; however if the precision is 0 or
missing, all characters in the string are printed.
% Print a `%'; no argument is used.
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.
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RETURN VALUES
Printf exits 0 on success, 1 on failure.
SEE ALSO
_p_r_i_n_t_f(3)
HISTORY
The printf command appeared in 4.3-Reno. It is modeled
after the standard library function, printf(3).
BUGS
Since the floating point numbers are translated from ASCII
to floating-point and then back again, floating-point preci-
sion may be lost.
ANSI hexadecimal character constants were deliberately not
provided.
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