diff options
Diffstat (limited to 'man3/sscanf.3')
| -rw-r--r-- | man3/sscanf.3 | 730 |
1 files changed, 0 insertions, 730 deletions
diff --git a/man3/sscanf.3 b/man3/sscanf.3 deleted file mode 100644 index 7e0198c..0000000 --- a/man3/sscanf.3 +++ /dev/null @@ -1,730 +0,0 @@ -'\" t -.\" Copyright (c) 1990, 1991 The Regents of the University of California. -.\" All rights reserved. -.\" -.\" This code is derived from software contributed to Berkeley by -.\" Chris Torek and the American National Standards Committee X3, -.\" on Information Processing Systems. -.\" -.\" SPDX-License-Identifier: BSD-4-Clause-UC -.\" -.\" @(#)scanf.3 6.14 (Berkeley) 1/8/93 -.\" -.\" Converted for Linux, Mon Nov 29 15:22:01 1993, faith@cs.unc.edu -.\" modified to resemble the GNU libio setup used in the Linux libc -.\" used in versions 4.x (x>4) and 5 Helmut.Geyer@iwr.uni-heidelberg.de -.\" Modified, aeb, 970121 -.\" 2005-07-14, mtk, added description of %n$ form; various text -.\" incorporated from the GNU C library documentation ((C) The -.\" Free Software Foundation); other parts substantially rewritten. -.\" -.\" 2008-06-23, mtk -.\" Add ERRORS section. -.\" Document the 'a' and 'm' modifiers for dynamic string allocation. -.\" -.TH sscanf 3 2023-12-09 "Linux man-pages 6.7" -.SH NAME -sscanf, vsscanf \- input string format conversion -.SH LIBRARY -Standard C library -.RI ( libc ", " \-lc ) -.SH SYNOPSIS -.nf -.B #include <stdio.h> -.P -.BI "int sscanf(const char *restrict " str , -.BI " const char *restrict " format ", ...);" -.P -.B #include <stdarg.h> -.P -.BI "int vsscanf(const char *restrict " str , -.BI " const char *restrict " format ", va_list " ap ); -.fi -.P -.RS -4 -Feature Test Macro Requirements for glibc (see -.BR feature_test_macros (7)): -.RE -.P -.BR vsscanf (): -.nf - _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L -.fi -.SH DESCRIPTION -The -.BR sscanf () -family of functions scans formatted input according to -.I format -as described below. -This format may contain -.IR "conversion specifications" ; -the results from such conversions, if any, -are stored in the locations pointed to by the -.I pointer -arguments that follow -.IR format . -Each -.I pointer -argument must be of a type that is appropriate for the value returned -by the corresponding conversion specification. -.P -If the number of conversion specifications in -.I format -exceeds the number of -.I pointer -arguments, the results are undefined. -If the number of -.I pointer -arguments exceeds the number of conversion specifications, then the excess -.I pointer -arguments are evaluated, but are otherwise ignored. -.P -.BR sscanf () -These functions -read their input from the string pointed to by -.IR str . -.P -The -.BR vsscanf () -function is analogous to -.BR vsprintf (3). -.P -The -.I format -string consists of a sequence of -.I directives -which describe how to process the sequence of input characters. -If processing of a directive fails, no further input is read, and -.BR sscanf () -returns. -A "failure" can be either of the following: -.IR "input failure" , -meaning that input characters were unavailable, or -.IR "matching failure" , -meaning that the input was inappropriate (see below). -.P -A directive is one of the following: -.TP -\[bu] -A sequence of white-space characters (space, tab, newline, etc.; see -.BR isspace (3)). -This directive matches any amount of white space, -including none, in the input. -.TP -\[bu] -An ordinary character (i.e., one other than white space or \[aq]%\[aq]). -This character must exactly match the next character of input. -.TP -\[bu] -A conversion specification, -which commences with a \[aq]%\[aq] (percent) character. -A sequence of characters from the input is converted according to -this specification, and the result is placed in the corresponding -.I pointer -argument. -If the next item of input does not match the conversion specification, -the conversion fails\[em]this is a -.IR "matching failure" . -.P -Each -.I conversion specification -in -.I format -begins with either the character \[aq]%\[aq] or the character sequence -"\fB%\fP\fIn\fP\fB$\fP" -(see below for the distinction) followed by: -.TP -\[bu] -An optional \[aq]*\[aq] assignment-suppression character: -.BR sscanf () -reads input as directed by the conversion specification, -but discards the input. -No corresponding -.I pointer -argument is required, and this specification is not -included in the count of successful assignments returned by -.BR scanf (). -.TP -\[bu] -For decimal conversions, an optional quote character (\[aq]). -This specifies that the input number may include thousands' -separators as defined by the -.B LC_NUMERIC -category of the current locale. -(See -.BR setlocale (3).) -The quote character may precede or follow the \[aq]*\[aq] -assignment-suppression character. -.TP -\[bu] -An optional \[aq]m\[aq] character. -This is used with string conversions -.RI ( %s , -.IR %c , -.IR %[ ), -and relieves the caller of the -need to allocate a corresponding buffer to hold the input: instead, -.BR sscanf () -allocates a buffer of sufficient size, -and assigns the address of this buffer to the corresponding -.I pointer -argument, which should be a pointer to a -.I "char\ *" -variable (this variable does not need to be initialized before the call). -The caller should subsequently -.BR free (3) -this buffer when it is no longer required. -.TP -\[bu] -An optional decimal integer which specifies the -.IR "maximum field width" . -Reading of characters stops either when this maximum is reached or -when a nonmatching character is found, whichever happens first. -Most conversions discard initial white space characters (the exceptions -are noted below), -and these discarded characters don't count toward the maximum field width. -String input conversions store a terminating null byte (\[aq]\e0\[aq]) -to mark the end of the input; -the maximum field width does not include this terminator. -.TP -\[bu] -An optional -.IR "type modifier character" . -For example, the -.B l -type modifier is used with integer conversions such as -.B %d -to specify that the corresponding -.I pointer -argument refers to a -.I "long" -rather than a pointer to an -.IR int . -.TP -\[bu] -A -.I "conversion specifier" -that specifies the type of input conversion to be performed. -.P -The conversion specifications in -.I format -are of two forms, either beginning with \[aq]%\[aq] or beginning with -"\fB%\fP\fIn\fP\fB$\fP". -The two forms should not be mixed in the same -.I format -string, except that a string containing -"\fB%\fP\fIn\fP\fB$\fP" -specifications can include -.B %% -and -.BR %* . -If -.I format -contains \[aq]%\[aq] -specifications, then these correspond in order with successive -.I pointer -arguments. -In the -"\fB%\fP\fIn\fP\fB$\fP" -form (which is specified in POSIX.1-2001, but not C99), -.I n -is a decimal integer that specifies that the converted input should -be placed in the location referred to by the -.IR n -th -.I pointer -argument following -.IR format . -.SS Conversions -The following -.I "type modifier characters" -can appear in a conversion specification: -.TP -.B h -Indicates that the conversion will be one of -\fBd\fP, \fBi\fP, \fBo\fP, \fBu\fP, \fBx\fP, \fBX\fP, or \fBn\fP -and the next pointer is a pointer to a -.I short -or -.I unsigned short -(rather than -.IR int ). -.TP -.B hh -As for -.BR h , -but the next pointer is a pointer to a -.I signed char -or -.IR "unsigned char" . -.TP -.B j -As for -.BR h , -but the next pointer is a pointer to an -.I intmax_t -or a -.IR uintmax_t . -This modifier was introduced in C99. -.TP -.B l -Indicates either that the conversion will be one of -\fBd\fP, \fBi\fP, \fBo\fP, \fBu\fP, \fBx\fP, \fBX\fP, or \fBn\fP -and the next pointer is a pointer to a -.I long -or -.I unsigned long -(rather than -.IR int ), -or that the conversion will be one of -\fBe\fP, \fBf\fP, or \fBg\fP -and the next pointer is a pointer to -.I double -(rather than -.IR float ). -If used with -.B %c -or -.BR %s , -the corresponding parameter is considered -as a pointer to a wide character or wide-character string respectively. -.\" This use of l was introduced in Amendment 1 to ISO C90. -.TP -.B ll -(ell-ell) -Indicates that the conversion will be one of -.BR b , -.BR d , -.BR i , -.BR o , -.BR u , -.BR x , -.BR X , -or -.B n -and the next pointer is a pointer to a -.I long long -or -.I unsigned long long -(rather than -.IR int ). -.TP -.B L -Indicates that the conversion will be either -\fBe\fP, \fBf\fP, or \fBg\fP -and the next pointer is a pointer to -.I "long double" -or -(as a GNU extension) -the conversion will be -\fBd\fP, \fBi\fP, \fBo\fP, \fBu\fP, or \fBx\fP -and the next pointer is a pointer to -.IR "long long" . -.\" MTK, Jul 05: The following is no longer true for modern -.\" ANSI C (i.e., C99): -.\" (Note that long long is not an -.\" ANSI C -.\" type. Any program using this will not be portable to all -.\" architectures). -.TP -.B q -equivalent to -.BR L . -This specifier does not exist in ANSI C. -.TP -.B t -As for -.BR h , -but the next pointer is a pointer to a -.IR ptrdiff_t . -This modifier was introduced in C99. -.TP -.B z -As for -.BR h , -but the next pointer is a pointer to a -.IR size_t . -This modifier was introduced in C99. -.P -The following -.I "conversion specifiers" -are available: -.TP -.B % -Matches a literal \[aq]%\[aq]. -That is, -.B %\&% -in the format string matches a -single input \[aq]%\[aq] character. -No conversion is done (but initial white space characters are discarded), -and assignment does not occur. -.TP -.B d -Matches an optionally signed decimal integer; -the next pointer must be a pointer to -.IR int . -.\" .TP -.\" .B D -.\" Equivalent to -.\" .IR ld ; -.\" this exists only for backward compatibility. -.\" (Note: thus only in libc4 -.\" In libc5 and glibc the -.\" .B %D -.\" is silently ignored, causing old programs to fail mysteriously.) -.TP -.B i -Matches an optionally signed integer; the next pointer must be a pointer to -.IR int . -The integer is read in base 16 if it begins with -.I 0x -or -.IR 0X , -in base 8 if it begins with -.IR 0 , -and in base 10 otherwise. -Only characters that correspond to the base are used. -.TP -.B o -Matches an unsigned octal integer; the next pointer must be a pointer to -.IR "unsigned int" . -.TP -.B u -Matches an unsigned decimal integer; the next pointer must be a -pointer to -.IR "unsigned int" . -.TP -.B x -Matches an unsigned hexadecimal integer -(that may optionally begin with a prefix of -.I 0x -or -.IR 0X , -which is discarded); the next pointer must -be a pointer to -.IR "unsigned int" . -.TP -.B X -Equivalent to -.BR x . -.TP -.B f -Matches an optionally signed floating-point number; the next pointer must -be a pointer to -.IR float . -.TP -.B e -Equivalent to -.BR f . -.TP -.B g -Equivalent to -.BR f . -.TP -.B E -Equivalent to -.BR f . -.TP -.B a -(C99) Equivalent to -.BR f . -.TP -.B s -Matches a sequence of non-white-space characters; -the next pointer must be a pointer to the initial element of a -character array that is long enough to hold the input sequence and -the terminating null byte (\[aq]\e0\[aq]), which is added automatically. -The input string stops at white space or at the maximum field -width, whichever occurs first. -.TP -.B c -Matches a sequence of characters whose length is specified by the -.I maximum field width -(default 1); the next pointer must be a pointer to -.IR char , -and there must be enough room for all the characters -(no terminating null byte is added). -The usual skip of leading white space is suppressed. -To skip white space first, use an explicit space in the format. -.TP -.B \&[ -Matches a nonempty sequence of characters from the specified set of -accepted characters; the next pointer must be a pointer to -.IR char , -and there must be enough room for all the characters in the string, plus a -terminating null byte. -The usual skip of leading white space is suppressed. -The string is to be made up of characters in (or not in) a particular set; -the set is defined by the characters between the open bracket -.B [ -character and a close bracket -.B ] -character. -The set -.I excludes -those characters if the first character after the open bracket is a -circumflex -.RB ( \[ha] ). -To include a close bracket in the set, make it the first character after -the open bracket or the circumflex; any other position will end the set. -The hyphen character -.B \- -is also special; when placed between two other characters, it adds all -intervening characters to the set. -To include a hyphen, make it the last -character before the final close bracket. -For instance, -.B [\[ha]]0\-9\-] -means -the set "everything except close bracket, zero through nine, and hyphen". -The string ends with the appearance of a character not in the (or, with a -circumflex, in) set or when the field width runs out. -.TP -.B p -Matches a pointer value (as printed by -.B %p -in -.BR printf (3)); -the next pointer must be a pointer to a pointer to -.IR void . -.TP -.B n -Nothing is expected; instead, the number of characters consumed thus far -from the input is stored through the next pointer, which must be a pointer -to -.IR int , -or variant whose size matches the (optionally) -supplied integer length modifier. -This is -.I not -a conversion and does -.I not -increase the count returned by the function. -The assignment can be suppressed with the -.B * -assignment-suppression character, but the effect on the -return value is undefined. -Therefore -.B %*n -conversions should not be used. -.SH RETURN VALUE -On success, these functions return the number of input items -successfully matched and assigned; -this can be fewer than provided for, -or even zero, in the event of an early matching failure. -.P -The value -.B EOF -is returned if the end of input is reached before either the first -successful conversion or a matching failure occurs. -.SH ERRORS -.TP -.B EILSEQ -Input byte sequence does not form a valid character. -.TP -.B EINVAL -Not enough arguments; or -.I format -is NULL. -.TP -.B ENOMEM -Out of memory. -.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 sscanf (), -.BR vsscanf () -T} Thread safety MT-Safe locale -.TE -.SH STANDARDS -C11, POSIX.1-2008. -.SH HISTORY -C89, POSIX.1-2001. -.P -The -.B q -specifier is the 4.4BSD notation for -.IR "long long" , -while -.B ll -or the usage of -.B L -in integer conversions is the GNU notation. -.P -The Linux version of these functions is based on the -.I GNU -.I libio -library. -Take a look at the -.I info -documentation of -.I GNU -.I libc (glibc-1.08) -for a more concise description. -.SH NOTES -.SS The 'a' assignment-allocation modifier -Originally, the GNU C library supported dynamic allocation for string inputs -(as a nonstandard extension) via the -.B a -character. -(This feature is present at least as far back as glibc 2.0.) -Thus, one could write the following to have -.BR sscanf () -allocate a buffer for a string, -with a pointer to that buffer being returned in -.IR *buf : -.P -.in +4n -.EX -char *buf; -sscanf(str, "%as", &buf); -.EE -.in -.P -The use of the letter -.B a -for this purpose was problematic, since -.B a -is also specified by the ISO C standard as a synonym for -.B f -(floating-point input). -POSIX.1-2008 instead specifies the -.B m -modifier for assignment allocation (as documented in DESCRIPTION, above). -.P -Note that the -.B a -modifier is not available if the program is compiled with -.I gcc\~\-std=c99 -or -.I gcc\~\-D_ISOC99_SOURCE -(unless -.B _GNU_SOURCE -is also specified), in which case the -.B a -is interpreted as a specifier for floating-point numbers (see above). -.P -Support for the -.B m -modifier was added to glibc 2.7, -and new programs should use that modifier instead of -.BR a . -.P -As well as being standardized by POSIX, the -.B m -modifier has the following further advantages over -the use of -.BR a : -.IP \[bu] 3 -It may also be applied to -.B %c -conversion specifiers (e.g., -.BR %3mc ). -.IP \[bu] -It avoids ambiguity with respect to the -.B %a -floating-point conversion specifier (and is unaffected by -.I gcc\~\-std=c99 -etc.). -.SH BUGS -.SS Numeric conversion specifiers -Use of the numeric conversion specifiers produces Undefined Behavior -for invalid input. -See -.UR https://port70.net/\:%7Ensz/\:c/\:c11/\:n1570.html\:#7.21.6.2p10 -C11 7.21.6.2/10 -.UE . -This is a bug in the ISO C standard, -and not an inherent design issue with the API. -However, -current implementations are not safe from that bug, -so it is not recommended to use them. -Instead, -programs should use functions such as -.BR strtol (3) -to parse numeric input. -Alternatively, -mitigate it by specifying a maximum field width. -.SS Nonstandard modifiers -These functions are fully C99 conformant, but provide the -additional modifiers -.B q -and -.B a -as well as an additional behavior of the -.B L -and -.B ll -modifiers. -The latter may be considered to be a bug, as it changes the -behavior of modifiers defined in C99. -.P -Some combinations of the type modifiers and conversion -specifiers defined by C99 do not make sense -(e.g., -.BR "%Ld" ). -While they may have a well-defined behavior on Linux, this need not -to be so on other architectures. -Therefore it usually is better to use -modifiers that are not defined by C99 at all, that is, use -.B q -instead of -.B L -in combination with -\fBd\fP, \fBi\fP, \fBo\fP, \fBu\fP, \fBx\fP, and \fBX\fP -conversions or -.BR ll . -.P -The usage of -.B q -is not the same as on 4.4BSD, -as it may be used in float conversions equivalently to -.BR L . -.SH EXAMPLES -To use the dynamic allocation conversion specifier, specify -.B m -as a length modifier (thus -.B %ms -or -\fB%m[\fP\fIrange\fP\fB]\fP). -The caller must -.BR free (3) -the returned string, as in the following example: -.P -.in +4n -.EX -char *p; -int n; -\& -errno = 0; -n = sscanf(str, "%m[a\-z]", &p); -if (n == 1) { - printf("read: %s\en", p); - free(p); -} else if (errno != 0) { - perror("sscanf"); -} else { - fprintf(stderr, "No matching characters\en"); -} -.EE -.in -.P -As shown in the above example, it is necessary to call -.BR free (3) -only if the -.BR sscanf () -call successfully read a string. -.SH SEE ALSO -.BR getc (3), -.BR printf (3), -.BR setlocale (3), -.BR strtod (3), -.BR strtol (3), -.BR strtoul (3) |