1994-05-27 05:00:24 +00:00
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.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Chris Torek and the American National Standards Committee X3,
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.\" on Information Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
|
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|
.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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|
.\" @(#)printf.3 8.1 (Berkeley) 6/4/93
|
1999-08-28 00:22:10 +00:00
|
|
|
.\" $FreeBSD$
|
1994-05-27 05:00:24 +00:00
|
|
|
.\"
|
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|
|
.Dd June 4, 1993
|
|
|
|
.Dt PRINTF 3
|
|
|
|
.Os
|
|
|
|
.Sh NAME
|
|
|
|
.Nm printf ,
|
|
|
|
.Nm fprintf ,
|
|
|
|
.Nm sprintf ,
|
|
|
|
.Nm snprintf ,
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
.Nm asprintf ,
|
1994-05-27 05:00:24 +00:00
|
|
|
.Nm vprintf ,
|
|
|
|
.Nm vfprintf,
|
|
|
|
.Nm vsprintf ,
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
.Nm vsnprintf ,
|
|
|
|
.Nm vasprintf
|
1994-05-27 05:00:24 +00:00
|
|
|
.Nd formatted output conversion
|
2000-04-21 09:42:15 +00:00
|
|
|
.Sh LIBRARY
|
|
|
|
.Lb libc
|
1994-05-27 05:00:24 +00:00
|
|
|
.Sh SYNOPSIS
|
|
|
|
.Fd #include <stdio.h>
|
|
|
|
.Ft int
|
|
|
|
.Fn printf "const char *format" ...
|
|
|
|
.Ft int
|
|
|
|
.Fn fprintf "FILE *stream" "const char *format" ...
|
|
|
|
.Ft int
|
|
|
|
.Fn sprintf "char *str" "const char *format" ...
|
|
|
|
.Ft int
|
|
|
|
.Fn snprintf "char *str" "size_t size" "const char *format" ...
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
.Ft int
|
|
|
|
.Fn asprintf "char **ret" "const char *format" ...
|
1994-05-27 05:00:24 +00:00
|
|
|
.Fd #include <stdarg.h>
|
|
|
|
.Ft int
|
|
|
|
.Fn vprintf "const char *format" "va_list ap"
|
|
|
|
.Ft int
|
|
|
|
.Fn vfprintf "FILE *stream" "const char *format" "va_list ap"
|
|
|
|
.Ft int
|
1997-03-19 00:52:58 +00:00
|
|
|
.Fn vsprintf "char *str" "const char *format" "va_list ap"
|
1994-05-27 05:00:24 +00:00
|
|
|
.Ft int
|
|
|
|
.Fn vsnprintf "char *str" "size_t size" "const char *format" "va_list ap"
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
.Ft int
|
|
|
|
.Fn vasprintf "char **ret" "const char *format" "va_list ap"
|
1994-05-27 05:00:24 +00:00
|
|
|
.Sh DESCRIPTION
|
|
|
|
The
|
|
|
|
.Fn printf
|
|
|
|
family of functions produces output according to a
|
|
|
|
.Fa format
|
|
|
|
as described below.
|
|
|
|
.Fn Printf
|
|
|
|
and
|
|
|
|
.Fn vprintf
|
|
|
|
write output to
|
2001-02-01 16:38:02 +00:00
|
|
|
.Em stdout ,
|
1994-05-27 05:00:24 +00:00
|
|
|
the standard output stream;
|
|
|
|
.Fn fprintf
|
|
|
|
and
|
|
|
|
.Fn vfprintf
|
|
|
|
write output to the given output
|
|
|
|
.Fa stream ;
|
|
|
|
.Fn sprintf ,
|
|
|
|
.Fn snprintf ,
|
|
|
|
.Fn vsprintf ,
|
|
|
|
and
|
|
|
|
.Fn vsnprintf
|
|
|
|
write to the character string
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
.Fa str ;
|
|
|
|
and
|
|
|
|
.Fn asprintf
|
|
|
|
and
|
|
|
|
.Fn vasprintf
|
|
|
|
dynamically allocate a new string with
|
1999-07-25 17:38:59 +00:00
|
|
|
.Xr malloc 3 .
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
.Pp
|
1994-05-27 05:00:24 +00:00
|
|
|
These functions write the output under the control of a
|
|
|
|
.Fa format
|
|
|
|
string that specifies how subsequent arguments
|
|
|
|
(or arguments accessed via the variable-length argument facilities of
|
|
|
|
.Xr stdarg 3 )
|
|
|
|
are converted for output.
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
.Pp
|
2001-06-05 04:22:30 +00:00
|
|
|
These functions return the number of characters printed
|
1994-05-27 05:00:24 +00:00
|
|
|
(not including the trailing
|
|
|
|
.Ql \e0
|
2001-05-30 23:47:14 +00:00
|
|
|
used to end output to strings),
|
|
|
|
except for
|
|
|
|
.Fn snprintf
|
|
|
|
and
|
|
|
|
.Fn vsnprintf ,
|
|
|
|
which return the number of characters that would have been printed if the
|
|
|
|
.Fa size
|
|
|
|
were unlimited
|
|
|
|
.Po
|
|
|
|
again, not including the final
|
|
|
|
.Ql \e0
|
|
|
|
.Pc .
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
.Pp
|
|
|
|
.Fn Asprintf
|
|
|
|
and
|
|
|
|
.Fn vasprintf
|
2001-01-01 05:19:52 +00:00
|
|
|
set
|
|
|
|
.Fa *ret
|
|
|
|
to be a pointer to a buffer sufficiently large to hold the formatted string.
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
This pointer should be passed to
|
|
|
|
.Xr free 3
|
|
|
|
to release the allocated storage when it is no longer needed.
|
|
|
|
If sufficient space cannot be allocated,
|
|
|
|
.Fn asprintf
|
|
|
|
and
|
|
|
|
.Fn vasprintf
|
|
|
|
will return -1 and set
|
|
|
|
.Fa ret
|
|
|
|
to be a NULL pointer.
|
|
|
|
.Pp
|
1994-05-27 05:00:24 +00:00
|
|
|
.Fn Snprintf
|
|
|
|
and
|
|
|
|
.Fn vsnprintf
|
2001-06-05 23:39:45 +00:00
|
|
|
will write at most
|
|
|
|
.Fa size Ns \-1
|
|
|
|
of the characters printed into the output string
|
|
|
|
(the
|
|
|
|
.Fa size Ns 'th
|
|
|
|
character then gets the terminating
|
|
|
|
.Ql \e0 ) ;
|
|
|
|
if the return value is greater than or equal to the
|
|
|
|
.Fa size
|
|
|
|
argument, the string was too short
|
|
|
|
and some of the printed characters were discarded.
|
2001-06-05 04:22:30 +00:00
|
|
|
The output is always null-terminated.
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
.Pp
|
1994-05-27 05:00:24 +00:00
|
|
|
.Fn Sprintf
|
|
|
|
and
|
|
|
|
.Fn vsprintf
|
|
|
|
effectively assume an infinite
|
|
|
|
.Fa size .
|
|
|
|
.Pp
|
|
|
|
The format string is composed of zero or more directives:
|
|
|
|
ordinary
|
|
|
|
.\" multibyte
|
|
|
|
characters (not
|
|
|
|
.Cm % ) ,
|
|
|
|
which are copied unchanged to the output stream;
|
|
|
|
and conversion specifications, each of which results
|
|
|
|
in fetching zero or more subsequent arguments.
|
|
|
|
Each conversion specification is introduced by
|
|
|
|
the character
|
|
|
|
.Cm % .
|
|
|
|
The arguments must correspond properly (after type promotion)
|
|
|
|
with the conversion specifier.
|
|
|
|
After the
|
|
|
|
.Cm % ,
|
|
|
|
the following appear in sequence:
|
|
|
|
.Bl -bullet
|
|
|
|
.It
|
1997-01-14 07:31:39 +00:00
|
|
|
An optional field, consisting of a decimal digit string followed by a
|
|
|
|
.Cm $ ,
|
|
|
|
specifying the next argument to access .
|
|
|
|
If this field is not provided, the argument following the last
|
|
|
|
argument accessed will be used.
|
|
|
|
Arguments are numbered starting at
|
|
|
|
.Cm 1 .
|
|
|
|
If unaccessed arguments in the format string are interspersed with ones that
|
|
|
|
are accessed the results will be indeterminate.
|
|
|
|
.It
|
1994-05-27 05:00:24 +00:00
|
|
|
Zero or more of the following flags:
|
|
|
|
.Bl -hyphen
|
|
|
|
.It
|
|
|
|
A
|
|
|
|
.Cm #
|
|
|
|
character
|
|
|
|
specifying that the value should be converted to an ``alternate form''.
|
|
|
|
For
|
|
|
|
.Cm c ,
|
|
|
|
.Cm d ,
|
|
|
|
.Cm i ,
|
|
|
|
.Cm n ,
|
|
|
|
.Cm p ,
|
|
|
|
.Cm s ,
|
|
|
|
and
|
|
|
|
.Cm u ,
|
|
|
|
conversions, this option has no effect.
|
|
|
|
For
|
|
|
|
.Cm o
|
|
|
|
conversions, the precision of the number is increased to force the first
|
|
|
|
character of the output string to a zero (except if a zero value is printed
|
|
|
|
with an explicit precision of zero).
|
|
|
|
For
|
|
|
|
.Cm x
|
|
|
|
and
|
|
|
|
.Cm X
|
|
|
|
conversions, a non-zero result has the string
|
|
|
|
.Ql 0x
|
|
|
|
(or
|
|
|
|
.Ql 0X
|
|
|
|
for
|
|
|
|
.Cm X
|
|
|
|
conversions) prepended to it.
|
|
|
|
For
|
|
|
|
.Cm e ,
|
|
|
|
.Cm E ,
|
|
|
|
.Cm f ,
|
|
|
|
.Cm g ,
|
|
|
|
and
|
|
|
|
.Cm G ,
|
|
|
|
conversions, the result will always contain a decimal point, even if no
|
|
|
|
digits follow it (normally, a decimal point appears in the results of
|
|
|
|
those conversions only if a digit follows).
|
|
|
|
For
|
|
|
|
.Cm g
|
|
|
|
and
|
|
|
|
.Cm G
|
|
|
|
conversions, trailing zeros are not removed from the result as they
|
|
|
|
would otherwise be.
|
|
|
|
.It
|
|
|
|
A zero
|
|
|
|
.Sq Cm \&0
|
|
|
|
character specifying zero padding.
|
|
|
|
For all conversions except
|
|
|
|
.Cm n ,
|
|
|
|
the converted value is padded on the left with zeros rather than blanks.
|
|
|
|
If a precision is given with a numeric conversion
|
1996-04-09 21:48:21 +00:00
|
|
|
.Pf ( Cm d ,
|
1994-05-27 05:00:24 +00:00
|
|
|
.Cm i ,
|
|
|
|
.Cm o ,
|
|
|
|
.Cm u ,
|
|
|
|
.Cm i ,
|
|
|
|
.Cm x ,
|
|
|
|
and
|
|
|
|
.Cm X ) ,
|
|
|
|
the
|
|
|
|
.Sq Cm \&0
|
|
|
|
flag is ignored.
|
|
|
|
.It
|
|
|
|
A negative field width flag
|
|
|
|
.Sq Cm \-
|
|
|
|
indicates the converted value is to be left adjusted on the field boundary.
|
|
|
|
Except for
|
|
|
|
.Cm n
|
|
|
|
conversions, the converted value is padded on the right with blanks,
|
|
|
|
rather than on the left with blanks or zeros.
|
|
|
|
A
|
|
|
|
.Sq Cm \-
|
|
|
|
overrides a
|
|
|
|
.Sq Cm \&0
|
|
|
|
if both are given.
|
|
|
|
.It
|
|
|
|
A space, specifying that a blank should be left before a positive number
|
|
|
|
produced by a signed conversion
|
|
|
|
.Pf ( Cm d ,
|
|
|
|
.Cm e ,
|
|
|
|
.Cm E ,
|
|
|
|
.Cm f ,
|
|
|
|
.Cm g ,
|
|
|
|
.Cm G ,
|
|
|
|
or
|
|
|
|
.Cm i ) .
|
|
|
|
.It
|
|
|
|
A
|
|
|
|
.Sq Cm +
|
|
|
|
character specifying that a sign always be placed before a
|
|
|
|
number produced by a signed conversion.
|
|
|
|
A
|
|
|
|
.Sq Cm +
|
|
|
|
overrides a space if both are used.
|
|
|
|
.El
|
|
|
|
.It
|
|
|
|
An optional decimal digit string specifying a minimum field width.
|
|
|
|
If the converted value has fewer characters than the field width, it will
|
|
|
|
be padded with spaces on the left (or right, if the left-adjustment
|
|
|
|
flag has been given) to fill out
|
|
|
|
the field width.
|
|
|
|
.It
|
|
|
|
An optional precision, in the form of a period
|
2000-12-29 14:08:20 +00:00
|
|
|
.Sq Cm .\&
|
1994-05-27 05:00:24 +00:00
|
|
|
followed by an
|
|
|
|
optional digit string. If the digit string is omitted, the precision
|
|
|
|
is taken as zero. This gives the minimum number of digits to appear for
|
|
|
|
.Cm d ,
|
|
|
|
.Cm i ,
|
|
|
|
.Cm o ,
|
|
|
|
.Cm u ,
|
|
|
|
.Cm x ,
|
|
|
|
and
|
|
|
|
.Cm X
|
|
|
|
conversions, the number of digits to appear after the decimal-point for
|
|
|
|
.Cm e ,
|
|
|
|
.Cm E ,
|
|
|
|
and
|
|
|
|
.Cm f
|
|
|
|
conversions, the maximum number of significant digits for
|
|
|
|
.Cm g
|
|
|
|
and
|
|
|
|
.Cm G
|
|
|
|
conversions, or the maximum number of characters to be printed from a
|
|
|
|
string for
|
|
|
|
.Cm s
|
|
|
|
conversions.
|
|
|
|
.It
|
|
|
|
The optional character
|
|
|
|
.Cm h ,
|
|
|
|
specifying that a following
|
|
|
|
.Cm d ,
|
|
|
|
.Cm i ,
|
|
|
|
.Cm o ,
|
|
|
|
.Cm u ,
|
|
|
|
.Cm x ,
|
|
|
|
or
|
|
|
|
.Cm X
|
|
|
|
conversion corresponds to a
|
|
|
|
.Em short int
|
|
|
|
or
|
|
|
|
.Em unsigned short int
|
|
|
|
argument, or that a following
|
|
|
|
.Cm n
|
|
|
|
conversion corresponds to a pointer to a
|
|
|
|
.Em short int
|
|
|
|
argument.
|
|
|
|
.It
|
|
|
|
The optional character
|
|
|
|
.Cm l
|
|
|
|
(ell) specifying that a following
|
|
|
|
.Cm d ,
|
|
|
|
.Cm i ,
|
|
|
|
.Cm o ,
|
|
|
|
.Cm u ,
|
|
|
|
.Cm x ,
|
|
|
|
or
|
|
|
|
.Cm X
|
|
|
|
conversion applies to a pointer to a
|
|
|
|
.Em long int
|
|
|
|
or
|
|
|
|
.Em unsigned long int
|
|
|
|
argument, or that a following
|
|
|
|
.Cm n
|
|
|
|
conversion corresponds to a pointer to a
|
|
|
|
.Em long int
|
|
|
|
argument.
|
|
|
|
.It
|
|
|
|
The optional character
|
|
|
|
.Cm q ,
|
|
|
|
specifying that a following
|
|
|
|
.Cm d ,
|
|
|
|
.Cm i ,
|
|
|
|
.Cm o ,
|
|
|
|
.Cm u ,
|
|
|
|
.Cm x ,
|
|
|
|
or
|
|
|
|
.Cm X
|
|
|
|
conversion corresponds to a
|
|
|
|
.Em quad int
|
|
|
|
or
|
|
|
|
.Em unsigned quad int
|
|
|
|
argument, or that a following
|
|
|
|
.Cm n
|
|
|
|
conversion corresponds to a pointer to a
|
|
|
|
.Em quad int
|
|
|
|
argument.
|
|
|
|
.It
|
|
|
|
The character
|
|
|
|
.Cm L
|
|
|
|
specifying that a following
|
|
|
|
.Cm e ,
|
|
|
|
.Cm E ,
|
|
|
|
.Cm f ,
|
|
|
|
.Cm g ,
|
|
|
|
or
|
|
|
|
.Cm G
|
|
|
|
conversion corresponds to a
|
|
|
|
.Em long double
|
2000-01-17 01:28:00 +00:00
|
|
|
argument.
|
1994-05-27 05:00:24 +00:00
|
|
|
.It
|
|
|
|
A character that specifies the type of conversion to be applied.
|
|
|
|
.El
|
|
|
|
.Pp
|
|
|
|
A field width or precision, or both, may be indicated by
|
|
|
|
an asterisk
|
|
|
|
.Ql *
|
1997-01-14 07:31:39 +00:00
|
|
|
or an asterisk followed by one or more decimal digits and a
|
|
|
|
.Ql $
|
1994-05-27 05:00:24 +00:00
|
|
|
instead of a
|
|
|
|
digit string.
|
|
|
|
In this case, an
|
|
|
|
.Em int
|
|
|
|
argument supplies the field width or precision.
|
|
|
|
A negative field width is treated as a left adjustment flag followed by a
|
|
|
|
positive field width; a negative precision is treated as though it were
|
|
|
|
missing.
|
1997-01-14 07:31:39 +00:00
|
|
|
If a single format directive mixes positional (nn$)
|
|
|
|
and non-positional arguments, the results are undefined.
|
1994-05-27 05:00:24 +00:00
|
|
|
.Pp
|
|
|
|
The conversion specifiers and their meanings are:
|
|
|
|
.Bl -tag -width "diouxX"
|
|
|
|
.It Cm diouxX
|
|
|
|
The
|
|
|
|
.Em int
|
|
|
|
(or appropriate variant) argument is converted to signed decimal
|
|
|
|
.Pf ( Cm d
|
|
|
|
and
|
|
|
|
.Cm i ) ,
|
|
|
|
unsigned octal
|
|
|
|
.Pq Cm o ,
|
|
|
|
unsigned decimal
|
|
|
|
.Pq Cm u ,
|
|
|
|
or unsigned hexadecimal
|
|
|
|
.Pf ( Cm x
|
|
|
|
and
|
|
|
|
.Cm X )
|
|
|
|
notation. The letters
|
|
|
|
.Cm abcdef
|
|
|
|
are used for
|
|
|
|
.Cm x
|
|
|
|
conversions; the letters
|
|
|
|
.Cm ABCDEF
|
|
|
|
are used for
|
1995-05-15 12:23:03 +00:00
|
|
|
.Cm X
|
1994-05-27 05:00:24 +00:00
|
|
|
conversions.
|
|
|
|
The precision, if any, gives the minimum number of digits that must
|
|
|
|
appear; if the converted value requires fewer digits, it is padded on
|
|
|
|
the left with zeros.
|
|
|
|
.It Cm DOU
|
|
|
|
The
|
|
|
|
.Em long int
|
|
|
|
argument is converted to signed decimal, unsigned octal, or unsigned
|
|
|
|
decimal, as if the format had been
|
|
|
|
.Cm ld ,
|
|
|
|
.Cm lo ,
|
|
|
|
or
|
|
|
|
.Cm lu
|
|
|
|
respectively.
|
|
|
|
These conversion characters are deprecated, and will eventually disappear.
|
|
|
|
.It Cm eE
|
|
|
|
The
|
|
|
|
.Em double
|
|
|
|
argument is rounded and converted in the style
|
|
|
|
.Sm off
|
|
|
|
.Pf [\-]d Cm \&. No ddd Cm e No \\*(Pmdd
|
|
|
|
.Sm on
|
|
|
|
where there is one digit before the
|
|
|
|
decimal-point character
|
|
|
|
and the number of digits after it is equal to the precision;
|
|
|
|
if the precision is missing,
|
|
|
|
it is taken as 6; if the precision is
|
|
|
|
zero, no decimal-point character appears.
|
|
|
|
An
|
|
|
|
.Cm E
|
|
|
|
conversion uses the letter
|
|
|
|
.Cm E
|
|
|
|
(rather than
|
|
|
|
.Cm e )
|
|
|
|
to introduce the exponent.
|
|
|
|
The exponent always contains at least two digits; if the value is zero,
|
|
|
|
the exponent is 00.
|
|
|
|
.It Cm f
|
|
|
|
The
|
|
|
|
.Em double
|
|
|
|
argument is rounded and converted to decimal notation in the style
|
|
|
|
.Sm off
|
|
|
|
.Pf [-]ddd Cm \&. No ddd ,
|
|
|
|
.Sm on
|
|
|
|
where the number of digits after the decimal-point character
|
|
|
|
is equal to the precision specification.
|
|
|
|
If the precision is missing, it is taken as 6; if the precision is
|
|
|
|
explicitly zero, no decimal-point character appears.
|
|
|
|
If a decimal point appears, at least one digit appears before it.
|
1999-08-08 11:00:01 +00:00
|
|
|
.It Cm gG
|
1994-05-27 05:00:24 +00:00
|
|
|
The
|
|
|
|
.Em double
|
|
|
|
argument is converted in style
|
|
|
|
.Cm f
|
|
|
|
or
|
|
|
|
.Cm e
|
|
|
|
(or
|
|
|
|
.Cm E
|
|
|
|
for
|
|
|
|
.Cm G
|
|
|
|
conversions).
|
|
|
|
The precision specifies the number of significant digits.
|
|
|
|
If the precision is missing, 6 digits are given; if the precision is zero,
|
|
|
|
it is treated as 1.
|
|
|
|
Style
|
|
|
|
.Cm e
|
|
|
|
is used if the exponent from its conversion is less than -4 or greater than
|
|
|
|
or equal to the precision.
|
|
|
|
Trailing zeros are removed from the fractional part of the result; a
|
|
|
|
decimal point appears only if it is followed by at least one digit.
|
|
|
|
.It Cm c
|
|
|
|
The
|
|
|
|
.Em int
|
|
|
|
argument is converted to an
|
|
|
|
.Em unsigned char ,
|
|
|
|
and the resulting character is written.
|
|
|
|
.It Cm s
|
|
|
|
The
|
|
|
|
.Dq Em char *
|
|
|
|
argument is expected to be a pointer to an array of character type (pointer
|
|
|
|
to a string).
|
|
|
|
Characters from the array are written up to (but not including)
|
|
|
|
a terminating
|
|
|
|
.Dv NUL
|
|
|
|
character;
|
|
|
|
if a precision is specified, no more than the number specified are
|
|
|
|
written.
|
|
|
|
If a precision is given, no null character
|
|
|
|
need be present; if the precision is not specified, or is greater than
|
|
|
|
the size of the array, the array must contain a terminating
|
|
|
|
.Dv NUL
|
|
|
|
character.
|
|
|
|
.It Cm p
|
|
|
|
The
|
|
|
|
.Dq Em void *
|
|
|
|
pointer argument is printed in hexadecimal (as if by
|
|
|
|
.Ql %#x
|
|
|
|
or
|
|
|
|
.Ql %#lx ) .
|
|
|
|
.It Cm n
|
|
|
|
The number of characters written so far is stored into the
|
|
|
|
integer indicated by the
|
|
|
|
.Dq Em int *
|
|
|
|
(or variant) pointer argument.
|
|
|
|
No argument is converted.
|
|
|
|
.It Cm %
|
|
|
|
A
|
|
|
|
.Ql %
|
2000-03-02 14:54:02 +00:00
|
|
|
is written.
|
|
|
|
No argument is converted.
|
2000-03-02 09:14:21 +00:00
|
|
|
The complete conversion specification
|
1994-05-27 05:00:24 +00:00
|
|
|
is
|
|
|
|
.Ql %% .
|
|
|
|
.El
|
|
|
|
.Pp
|
2001-02-10 06:32:03 +00:00
|
|
|
The decimal point
|
2001-02-10 10:26:52 +00:00
|
|
|
character is defined in the program's locale (category
|
|
|
|
.Dv LC_NUMERIC ) .
|
2001-02-10 06:32:03 +00:00
|
|
|
.Pp
|
1994-05-27 05:00:24 +00:00
|
|
|
In no case does a non-existent or small field width cause truncation of
|
|
|
|
a field; if the result of a conversion is wider than the field width, the
|
|
|
|
field is expanded to contain the conversion result.
|
|
|
|
.Pp
|
|
|
|
.Sh EXAMPLES
|
|
|
|
To print a date and time in the form `Sunday, July 3, 10:02',
|
|
|
|
where
|
|
|
|
.Em weekday
|
|
|
|
and
|
|
|
|
.Em month
|
|
|
|
are pointers to strings:
|
|
|
|
.Bd -literal -offset indent
|
|
|
|
#include <stdio.h>
|
|
|
|
fprintf(stdout, "%s, %s %d, %.2d:%.2d\en",
|
|
|
|
weekday, month, day, hour, min);
|
|
|
|
.Ed
|
|
|
|
.Pp
|
|
|
|
To print \*(Pi
|
|
|
|
to five decimal places:
|
|
|
|
.Bd -literal -offset indent
|
|
|
|
#include <math.h>
|
|
|
|
#include <stdio.h>
|
|
|
|
fprintf(stdout, "pi = %.5f\en", 4 * atan(1.0));
|
|
|
|
.Ed
|
|
|
|
.Pp
|
|
|
|
To allocate a 128 byte string and print into it:
|
|
|
|
.Bd -literal -offset indent
|
|
|
|
#include <stdio.h>
|
|
|
|
#include <stdlib.h>
|
|
|
|
#include <stdarg.h>
|
|
|
|
char *newfmt(const char *fmt, ...)
|
|
|
|
{
|
|
|
|
char *p;
|
|
|
|
va_list ap;
|
|
|
|
if ((p = malloc(128)) == NULL)
|
|
|
|
return (NULL);
|
|
|
|
va_start(ap, fmt);
|
|
|
|
(void) vsnprintf(p, 128, fmt, ap);
|
|
|
|
va_end(ap);
|
|
|
|
return (p);
|
|
|
|
}
|
|
|
|
.Ed
|
|
|
|
.Sh SEE ALSO
|
|
|
|
.Xr printf 1 ,
|
|
|
|
.Xr scanf 3
|
|
|
|
.Sh STANDARDS
|
|
|
|
The
|
|
|
|
.Fn fprintf ,
|
|
|
|
.Fn printf ,
|
|
|
|
.Fn sprintf ,
|
|
|
|
.Fn vprintf ,
|
|
|
|
.Fn vfprintf ,
|
|
|
|
and
|
|
|
|
.Fn vsprintf
|
|
|
|
functions
|
|
|
|
conform to
|
2001-06-05 04:22:30 +00:00
|
|
|
.St -ansiC
|
|
|
|
and
|
|
|
|
.St -isoC-99 .
|
|
|
|
The
|
|
|
|
.Fn snprintf
|
|
|
|
and
|
|
|
|
.Fn vsnprintf
|
|
|
|
functions conform to
|
|
|
|
.St -isoC-99 .
|
1994-05-27 05:00:24 +00:00
|
|
|
.Sh HISTORY
|
|
|
|
The functions
|
Add an implementation of the gnu-ish asprintf() and vasprintf(). They are
not based on gpl'ed code, just prototype and usage. I'm not 100% certain
they behave the same while the system is in trouble (eg: malloc() failing)
but in those circumstances all bets would be off anyway.
These routines work like sprintf() and vsprintf(), except that instead of
using a fixed buffer, they allocate memory and return it to the user
and it's the user's responsibility to free() it. They have allocate as
much memory as they need (and can get), so the size of strings it can deal
with is limited only by the amount of memory it can malloc() on your
behalf.
There are a few gpl'ed programs starting to use this interface, and it's
becoming more common with the scares about security risks with sprintf().
I dont like the look of the code that the various programs (including
cvs, gdb, libg++, etc) provide if configure can't find it on the system.
It should be possible to modify the stdio core code to provide this
interface more efficiently, I was more worried about having something
that worked and was secure. :-) (I noticed that there was once intended
to be a smprintf() routine when our stdio was written for 4.4BSD, but it
looks pretty stillborn, and it's intended interface is not clear). Since
Linux and gnu libc have this interface, it seemed silly to bring yet
another one onto the scene.
1996-05-27 10:49:43 +00:00
|
|
|
.Fn asprintf
|
|
|
|
and
|
|
|
|
.Fn vasprintf
|
1998-07-08 00:44:56 +00:00
|
|
|
first appeared in the GNU C library.
|
2001-04-18 13:16:47 +00:00
|
|
|
These were implemented by
|
|
|
|
.An Peter Wemm Aq peter@FreeBSD.org
|
|
|
|
in
|
1998-07-08 00:44:56 +00:00
|
|
|
.Fx 2.2 ,
|
|
|
|
but were later replaced with a different implementation
|
2001-04-18 13:16:47 +00:00
|
|
|
from
|
|
|
|
.An Todd C. Miller Aq Todd.Miller@courtesan.com
|
|
|
|
for
|
1998-07-08 00:44:56 +00:00
|
|
|
.Ox 2.3 .
|
1994-05-27 05:00:24 +00:00
|
|
|
.Sh BUGS
|
|
|
|
The conversion formats
|
|
|
|
.Cm \&%D ,
|
|
|
|
.Cm \&%O ,
|
|
|
|
and
|
|
|
|
.Cm %U
|
|
|
|
are not standard and
|
|
|
|
are provided only for backward compatibility.
|
|
|
|
The effect of padding the
|
|
|
|
.Cm %p
|
|
|
|
format with zeros (either by the
|
|
|
|
.Sq Cm 0
|
|
|
|
flag or by specifying a precision), and the benign effect (i.e., none)
|
|
|
|
of the
|
|
|
|
.Sq Cm #
|
|
|
|
flag on
|
|
|
|
.Cm %n
|
|
|
|
and
|
|
|
|
.Cm %p
|
|
|
|
conversions, as well as other
|
|
|
|
nonsensical combinations such as
|
|
|
|
.Cm %Ld ,
|
|
|
|
are not standard; such combinations
|
|
|
|
should be avoided.
|
|
|
|
.Pp
|
|
|
|
Because
|
|
|
|
.Fn sprintf
|
|
|
|
and
|
|
|
|
.Fn vsprintf
|
|
|
|
assume an infinitely long string,
|
|
|
|
callers must be careful not to overflow the actual space;
|
1996-06-09 06:48:42 +00:00
|
|
|
this is often hard to assure.
|
1994-05-27 05:00:24 +00:00
|
|
|
For safety, programmers should use the
|
|
|
|
.Fn snprintf
|
|
|
|
interface instead.
|
2001-06-05 04:22:30 +00:00
|
|
|
Unfortunately, this interface was only defined in
|
|
|
|
.St -isoC-99 .
|
|
|
|
.Pp
|
|
|
|
.Cm %n
|
|
|
|
can be used to write arbitrary data to the stack.
|
|
|
|
Programmers are therefore strongly advised to never pass untrusted strings
|
|
|
|
as the
|
|
|
|
.Fa format
|
|
|
|
argument.
|
2001-05-25 20:42:40 +00:00
|
|
|
.Pp
|
|
|
|
Never pass a string with user-supplied data as a format without using
|
|
|
|
.Ql %s .
|
|
|
|
An attacker can put format specifiers in the string to mangle your stack,
|
|
|
|
leading to a possible security hole.
|
|
|
|
This holds true even if the string was built using a function like
|
|
|
|
.Fn snprintf ,
|
|
|
|
as the resulting string may still contain user-supplied conversion specifiers
|
|
|
|
for later interpolation by
|
|
|
|
.Fn printf .
|
|
|
|
.Pp
|
|
|
|
Always use the proper secure idiom:
|
|
|
|
.Pp
|
|
|
|
.Dl snprintf(buffer, sizeof(buffer), "%s", string);
|