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printf.3: Merge dprintf() and vdprintf() discussion into this page 

Reported-by: Egmont Koblinger <egmont@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Michael Kerrisk 2015-04-27 15:47:37 +02:00
parent c14e2adc7c
commit 62730046cc
1 changed files with 43 additions and 6 deletions
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49
man3/printf.3
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@ -33,8 +33,8 @@
.\"
.TH PRINTF 3 2015-04-19 "GNU" "Linux Programmer's Manual"
.SH NAME
printf, fprintf, sprintf, snprintf, vprintf, vfprintf, vsprintf,
vsnprintf \- formatted output conversion
printf, fprintf, dprintf, sprintf, snprintf, vprintf, vfprintf, vdprintf,
vsprintf, vsnprintf \- formatted output conversion
.SH SYNOPSIS
.B #include <stdio.h>
.sp
@ -42,6 +42,8 @@ vsnprintf \- formatted output conversion
.br
.BI "int fprintf(FILE *" stream ", const char *" format ", ...);"
.br
.BI "int dprintf(int " fd ", const char *" format ", ...);"
.br
.BI "int sprintf(char *" str ", const char *" format ", ...);"
.br
.BI "int snprintf(char *" str ", size_t " size ", const char *" format ", ...);"
@ -52,6 +54,8 @@ vsnprintf \- formatted output conversion
.br
.BI "int vfprintf(FILE *" stream ", const char *" format ", va_list " ap );
.br
.BI "int vdprintf(int " fd ", const char *" format ", va_list " ap );
.br
.BI "int vsprintf(char *" str ", const char *" format ", va_list " ap );
.br
.BI "int vsnprintf(char *" str ", size_t " size ", const char *" format \
@ -72,7 +76,20 @@ _POSIX_C_SOURCE\ >=\ 200112L;
or
.I "cc -std=c99"
.RE
.sp
.BR dprintf (),
.BR vdprintf ():
.PD 0
.RS 4
.TP 4
Since glibc 2.10:
_XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
.TP
Before glibc 2.10:
_GNU_SOURCE
.RE
.ad
.PD
.SH DESCRIPTION
The functions in the
.BR printf ()
@ -98,7 +115,17 @@ and
.BR vsnprintf ()
write to the character string
.IR str .
.PP
The function
.BR dprintf ()
is the same as
.BR fprintf (3)
except that it outputs to a file descriptor,
.IR fd ,
instead of to a
.I stdio
stream.
The functions
.BR snprintf ()
and
@ -107,15 +134,17 @@ write at most
.I size
bytes (including the terminating null byte (\(aq\e0\(aq)) to
.IR str .
.PP
The functions
.BR vprintf (),
.BR vfprintf (),
.BR vdprintf (),
.BR vsprintf (),
.BR vsnprintf ()
are equivalent to the functions
.BR printf (),
.BR fprintf (),
.BR dprintf (),
.BR sprintf (),
.BR snprintf (),
respectively, except that they are called with a
@ -131,8 +160,8 @@ macro, the value of
is undefined after the call.
See
.BR stdarg (3).
.PP
These eight functions write the output under the control of a
All of these functions write the output under the control of a
.I format
string that specifies how subsequent arguments (or arguments accessed via
the variable-length argument facilities of
@ -855,11 +884,19 @@ The
and
.BR vsprintf ()
functions conform to C89 and C99.
The
.BR snprintf ()
and
.BR vsnprintf ()
functions conform to C99.
The
.BR dprintf ()
and
.BR vdprintf ()
functions were originally GNU extensions that were later standardized
in POSIX.1-2008.
.PP
Concerning the return value of
.BR snprintf (),