diff options
Diffstat (limited to 'man3/printf.3')
| -rw-r--r-- | man3/printf.3 | 166 |
1 files changed, 97 insertions, 69 deletions
diff --git a/man3/printf.3 b/man3/printf.3 index 33fe60067..edd6ba85a 100644 --- a/man3/printf.3 +++ b/man3/printf.3 @@ -13,7 +13,7 @@ .\" 2000-07-26 jsm28@hermes.cam.ac.uk - three small fixes .\" 2000-10-16 jsm28@hermes.cam.ac.uk - more fixes .\" -.TH printf 3 2023-02-05 "Linux man-pages 6.03" +.TH printf 3 2023-07-20 "Linux man-pages 6.05.01" .SH NAME printf, fprintf, dprintf, sprintf, snprintf, vprintf, vfprintf, vdprintf, vsprintf, vsnprintf \- formatted output conversion @@ -324,7 +324,7 @@ and flags both appear, the .B \&0 flag is ignored. -If a precision is given with a numeric conversion +If a precision is given with an integer conversion .RB ( d , .BR i , .BR o , @@ -895,7 +895,92 @@ or more means that the output was truncated. (See also below under NOTES.) .PP If an output error is encountered, a negative value is returned. -.SH VERSIONS +.SH ATTRIBUTES +For an explanation of the terms used in this section, see +.BR attributes (7). +.TS +allbox; +lbx lb lb +l l l. +Interface Attribute Value +T{ +.na +.nh +.BR printf (), +.BR fprintf (), +.BR sprintf (), +.BR snprintf (), +.BR vprintf (), +.BR vfprintf (), +.BR vsprintf (), +.BR vsnprintf () +T} Thread safety MT-Safe locale +.TE +.sp 1 +.SH STANDARDS +.TP +.BR fprintf () +.TQ +.BR printf () +.TQ +.BR sprintf () +.TQ +.BR vprintf () +.TQ +.BR vfprintf () +.TQ +.BR vsprintf () +.TQ +.BR snprintf () +.TQ +.BR vsnprintf () +C11, POSIX.1-2008. +.TP +.BR dprintf () +.TQ +.BR vdprintf () +GNU, POSIX.1-2008. +.SH HISTORY +.TP +.BR fprintf () +.TQ +.BR printf () +.TQ +.BR sprintf () +.TQ +.BR vprintf () +.TQ +.BR vfprintf () +.TQ +.BR vsprintf () +C89, POSIX.1-2001. +.TP +.BR snprintf () +.TQ +.BR vsnprintf () +SUSv2, C99, POSIX.1-2001. +.IP +Concerning the return value of +.BR snprintf (), +SUSv2 and C99 contradict each other: when +.BR snprintf () +is called with +.IR size =0 +then SUSv2 stipulates an unspecified return value less than 1, +while C99 allows +.I str +to be NULL in this case, and gives the return value (as always) +as the number of characters that would have been written in case +the output string has been large enough. +POSIX.1-2001 and later align their specification of +.BR snprintf () +with C99. +.TP +.BR dprintf () +.TQ +.BR vdprintf () +GNU, POSIX.1-2008. +.PP .\" Linux libc4 knows about the five C standard flags. .\" It knows about the length modifiers \fBh\fP, \fBl\fP, \fBL\fP, .\" and the conversions @@ -935,64 +1020,7 @@ of the .B m conversion specifier, that is .IR %#m . -.SH ATTRIBUTES -For an explanation of the terms used in this section, see -.BR attributes (7). -.ad l -.nh -.TS -allbox; -lbx lb lb -l l l. -Interface Attribute Value -T{ -.BR printf (), -.BR fprintf (), -.BR sprintf (), -.BR snprintf (), -.BR vprintf (), -.BR vfprintf (), -.BR vsprintf (), -.BR vsnprintf () -T} Thread safety MT-Safe locale -.TE -.hy -.ad -.sp 1 -.SH STANDARDS -.BR fprintf (), -.BR printf (), -.BR sprintf (), -.BR snprintf (), -.BR vprintf (), -.BR vfprintf (), -.BR vsprintf (), -.BR vsnprintf (): -POSIX.1-2001, POSIX.1-2008, C99. -.PP -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 (), -SUSv2 and C99 contradict each other: when -.BR snprintf () -is called with -.IR size =0 -then SUSv2 stipulates an unspecified return value less than 1, -while C99 allows -.I str -to be NULL in this case, and gives the return value (as always) -as the number of characters that would have been written in case -the output string has been large enough. -POSIX.1-2001 and later align their specification of -.BR snprintf () -with C99. -.SH NOTES +.SH CAVEATS Some programs imprudently rely on code such as the following .PP .in +4n @@ -1162,7 +1190,7 @@ To allocate a sufficiently large string and print into it #include <stdio.h> #include <stdlib.h> #include <stdarg.h> - +\& char * make_message(const char *fmt, ...) { @@ -1170,30 +1198,30 @@ make_message(const char *fmt, ...) size_t size = 0; char *p = NULL; va_list ap; - +\& /* Determine required size. */ - +\& va_start(ap, fmt); n = vsnprintf(p, size, fmt, ap); va_end(ap); - +\& if (n < 0) return NULL; - +\& size = (size_t) n + 1; /* One extra byte for \[aq]\e0\[aq] */ p = malloc(size); if (p == NULL) return NULL; - +\& va_start(ap, fmt); n = vsnprintf(p, size, fmt, ap); va_end(ap); - +\& if (n < 0) { free(p); return NULL; } - +\& return p; } .EE |