| Previous | Contents | Index |
Running the example program produces the following result:
Successfully converted <Thursday 01 January 1970 00:08:20> Successfully converted <Tuesday 29 February 1972 08:26:40> Successfully converted <Tuesday 31 December 1991 23:59:59> Successfully converted <Wednesday 01 January 1992 00:00:00> Successfully converted <Sunday 03 May 1992 13:33:20> Successfully converted <Monday 04 May 1992 17:20:00> Successfully converted <Friday 15 May 1992 03:20:00> |
Returns the address of the last occurrence of a given character in a null-terminated string.
#include <string.h>Function Variants The strrchr function has variants named _strrchr32 and _strrchr64 for use with 32-bit and 64-bit pointer sizes, respectively. See Section 1.10 for more information on using pointer-size-specific functions.char *strrchr (const char *str, int character);
str
A pointer to a null-terminated character string.character
An object of type int .
This function returns the address of the last occurrence of a given character in a null-terminated string. The terminating null character is considered to be part of the string.Compare with strchr , which returns the address of the first occurrence of a given character in a null-terminated string.
x The address of the last occurrence of the specified character. NULL Indicates that the character does not occur in the string.
Separates strings.
#include <string.h>Function Variants The strsep function has variants named _strsep32 and _strsep64 for use with 32-bit and 64-bit pointer sizes, respectively. See Section 1.10 for more information on using pointer-size-specific functions.char *strsep (char **stringp, char *delim);
stringp
A pointer to a pointer to a character string.delim
A pointer to a string containing characters to be used as delimiters.
The strsep function locates in stringp, the first occurrence of any character in delim (or the terminating '\0' character) and replaces it with a '\0'. The location of the next character after the delimiter character (or NULL, if the end of the string is reached) is stored in the stringp argument. The original value of the stringp argument is returned.You can detect an "empty" field; one caused by two adjacent delimiter characters, by comparing the location referenced by the pointer returned in the stringp argument to '\0'.
The stringp argument is initially NULL, strsep returns NULL.
x The address of the string pointed to by stringp. NULL Indicates that stringp is NULL.
The following example uses strsep to parse a string, containing token delimited by white space, into an argument vector:
char **ap, **argv[10], *inputstring; for (ap = argv; (*ap = strsep(&inputstring, " \t")) != NULL;) if (**ap != '\0') ++ap;
Returns the length of the prefix of a string that consists entirely of characters from a set of characters.
#include <string.h>size_t strspn (const char *str, const char *charset);
str
A pointer to a character string. If this string is a null string, 0 is returned.charset
A pointer to a character string containing the characters for which the function will search.
The strspn function scans the characters in the string, stops when it encounters a character not found in charset, and returns the length of the string's initial segment formed by characters found in charset.
x The length of the segment.
Locates the first occurrence in the string pointed to by s1 of the sequence of characters in the string pointed to by s2.
#include <string.h>Function Variants The strstr function has variants named _strstr32 and _strstr64 for use with 32-bit and 64-bit pointer sizes, respectively. See Section 1.10 for more information on using pointer-size-specific functions.char *strstr (const char *s1, const char *s2);
s1, s2
Pointers to character strings.
Pointer A pointer to the located string. NULL Indicates that the string was not found.
#include <stdlib.h> #include <stdio.h> #include <string.h> main() { static char lookin[]="that this is a test was at the end"; putchar('\n'); printf("String: %s\n", &lookin[0] ); putchar('\n'); printf("Addr: %s\n", &lookin[0] ); printf("this: %s\n", strstr( &lookin[0] ,"this") ); printf("that: %s\n", strstr( &lookin[0] , "that" ) ); printf("NULL: %s\n", strstr( &lookin[0], "" ) ); printf("was: %s\n", strstr( &lookin[0], "was" ) ); printf("at: %s\n", strstr( &lookin[0], "at" ) ); printf("the end: %s\n", strstr( &lookin[0], "the end") ); putchar('\n'); exit(0); }
This example produces the following results:
$ RUN STRSTR_EXAMPLE String: that this is a test was at the end Addr: that this is a test was at the end this: this is a test was at the end that: that this is a test was at the end NULL: that this is a test was at the end was: was at the end at: at this is a test was at the end the end: the end $ |
Converts a given string to a double-precision number.
#include <stdlib.h>Function Variants The strtod function has variants named _strtod32 and _strtod64 for use with 32-bit and 64-bit pointer sizes, respectively. See Section 1.10 for more information on using pointer-size-specific functions.double strtod (const char *nptr, char **endptr);
nptr
A pointer to the character string to be converted to a double-precision number.endptr
The address of an object where the function can store the address of the first unrecognized character that terminates the scan. If endptr is a NULL pointer, the address of the first unrecognized character is not retained.
The strtod function recognizes an optional sequence of white-space characters (as defined by isspace ), then an optional plus or minus sign, then a sequence of digits optionally containing a radix character, then an optional letter (e or E) followed by an optionally signed integer. The first unrecognized character ends the conversion.The string is interpreted by the same rules used to interpret floating constants.
The radix character is defined the program's current locale (category LC_NUMERIC).
This function returns the converted value. For strtod , overflows are accounted for in the following manner:
- If the correct value causes an overflow, HUGE_VAL (with a plus or minus sign according to the sign of the value) is returned and errno is set to ERANGE.
- If the correct value causes an underflow, 0 is returned and errno is set to ERANGE.
If the string starts with an unrecognized character, then the conversion is not performed, *endptr is set to nptr, a 0 value is returned, and errno is set to EINVAL.)
x The converted string. 0 Indicates the conversion could not be performed. errno is set to one of the following:
- EINVAL - No conversion could be performed.
- ERANGE - The value would cause an underflow.
- ENOMEM - Not enough memory available for internal conversion buffer.
±HUGE_VAL Overflow occurred; errno is set to ERANGE.
Split strings into tokens.
#include <string.h>Function Variants The strtok function has variants named _strtok32 and _strtok64 for use with 32-bit and 64-bit pointer sizes, respectively. Likewise, the strtok_r function has variants named _strtok_r32 and _strtok_r64 . See Section 1.10 for more information on using pointer-size-specific functions.char *strtok (char *s1, const char *s2);
char *strtok_r (char *s, const char *sep, char **lasts);
s1
On the first call, a pointer to a string containing zero or more text tokens. On all subsequent calls for that string, a NULL pointer.s2
A pointer to a separator string consisting of one or more characters. The separator string may differ from call to call.s
A null-terminated string that is a sequence of zero or more text tokens separated by spans of one or more characters from the separator string sep.sep
A null-terminated string of separator characters. This separator string can be different from call to call.lasts
A pointer that points to a user-provided pointer to stored information needed for strtok_r to continue scanning the same string.
The strtok function locates text tokens in a given string. The text tokens are delimited by one or more characters from a separator string that you specify. The function keeps track of its position in the string between calls and, as successive calls are made, the function works through the string, identifying the text token following the one identified by the previous call.A token in s1 starts at the first character that is not a character in the separator string s2 and ends either at the end of the string or at (but not including) a separator character.
The first call to the strtok function returns a pointer to the first character in the first token and writes a null character into s1 immediately following the returned token. Each subsequent call (with the value of the first argument remaining NULL) returns a pointer to a subsequent token in the string originally pointed to by s1. When no tokens remain in the string, the strtok function returns a NULL pointer. (This can occur on the first call to strtok if the string is empty or contains only separator characters.)
Since strtok inserts null characters into s1 to delimit tokens, s1 cannot be a const object.
The strtok_r function is the reentrant version of strtok . The function strtok_r considers the null-terminated string s as a sequence of zero or more text tokens separated by spans of one or more characters from the separator string sep. The lasts argument points to a user-provided pointer to stored information needed for strtok_r to continue scanning the same string.
In the first call to strtok_r , s points to a null-terminated string, sep points to a null-terminated string of separator characters, and the value pointed to by lasts is ignored. The strtok_r function returns a pointer to the first character of the first token, writes a null character into s immediately following the returned token, and updates the pointer to which lasts points.
In subsequent calls, s is a NULL pointer and lasts is unchanged from the previous call so that subsequent calls move through the string s, returning successive tokens until no tokens remain. The separator string sep can be different from call to call. When no token remains in s, a NULL pointer is returned.
x A pointer to the first character of the parsed token in the string. NULL Indicates that there are no tokens remaining in the string.
| #1 |
|---|
#include <stdio.h>
#include <string.h>
main()
{
static char str[] = "...ab..cd,,ef.hi";
printf("|%s|\n", strtok(str, "."));
printf("|%s|\n", strtok(NULL, ","));
printf("|%s|\n", strtok(NULL, ",."));
printf("|%s|\n", strtok(NULL, ",."));
}
|
Running this example program produces the following results:
$ RUN STRTOK_EXAMPLE1 |ab| |.cd| |ef| |hi| $
| #2 |
|---|
#include <stdio.h>
#include <string.h>
main()
{
char *ptr,
string[30];
/* The first character not in the string "-" is "A". The */
/* token ends at "C. */
strcpy(string, "ABC");
ptr = strtok(string, "-");
printf("|%s|\n", ptr);
/* Returns NULL because no characters not in separator */
/* string "-" were found (i.e. only separator characters */
/* were found) */
strcpy(string, "-");
ptr = strtok(string, "-");
if (ptr == NULL)
printf("ptr is NULL\n");
}
|
Running this example program produces the following results:
$ RUN STRTOK_EXAMPLE2 |abc| ptr is NULL $
Converts strings of ASCII characters to the appropriate numeric values.
#include <stdlib.h>Function Variants The strtol function has variants named _strtol32 and _strtol64 for use with 32-bit and 64-bit pointer sizes, respectively. See Section 1.10 for more information on using pointer-size-specific functions.long int strtol (const char *nptr, char **endptr, int base);
nptr
A pointer to the character string to be converted to a long .endptr
The address of an object where the function can store a pointer to the first unrecognized character encountered in the conversion process (that is, the character that follows the last character in the string being converted). If endptr is a NULL pointer, the address of the first unrecognized character is not retained.base
The value, 2 through 36, to use as the base for the conversion.
The strtol function recognizes strings in various formats, depending on the value of the base. This function ignores any leading white-space characters (as defined by isspace in <ctype.h> ) in the given string. It recognizes an optional plus or minus sign, then a sequence of digits or letters that may represent an integer constant according to the value of the base. The first unrecognized character ends the conversion.Leading zeros after the optional sign are ignored, and 0x or 0X is ignored if the base is 16.
If base is 0, the sequence of characters is interpreted by the same rules used to interpret an integer constant: after the optional sign, a leading 0 indicates octal conversion, a leading 0x or 0X indicates hexadecimal conversion, and any other combination of leading characters indicates decimal conversion.
Truncation from long to int can take place after assignment or by an explicit cast (arithmetic exceptions not withstanding). The function call atol (str) is equivalent to strtol (str, (char**)NULL, 10) .
x The converted value. LONG_MAX or LONG_MIN Indicates that the converted value would cause an overflow. 0 Indicates that the string starts with an unrecognized character or that the value for base is invalid. If the string starts with an unrecognized character, * endptr is set to nptr.
Convert strings of ASCII characters to the appropriate numeric values. strtoll is a synonym for strtoq .
#include <stdlib.h>Function Variants These functions have variants named _strtoq32 , _strtoll32 and _strtoq64 , _strtoll64 for use with 32-bit and 64-bit pointer sizes, respectively. See Section 1.10 for more information on using pointer-size-specific functions.__int64 strtoq (const char *nptr, char **endptr, int base);
__int64 strtoll (const char *nptr, char **endptr, int base);
nptr
A pointer to the character string to be converted to an __int64 .endptr
The address of an object where the function can store a pointer to the first unrecognized character encountered in the conversion process (that is, the character that follows the last character in the string being converted). If endptr is a NULL pointer, the address of the first unrecognized character is not retained.base
The value, 2 through 36, to use as the base for the conversion.
The strtoq and strtoll functions recognize strings in various formats, depending on the value of the base. Any leading white-space characters (as defined by isspace in <ctype.h> ) in the given string are ignored. The functions recognize an optional plus or minus sign, then a sequence of digits or letters that may represent an integer constant according to the value of the base. The first unrecognized character ends the conversion.Leading zeros after the optional sign are ignored, and 0x or 0X is ignored if the base is 16.
If base is 0, the sequence of characters is interpreted by the same rules used to interpret an integer constant: after the optional sign, a leading 0 indicates octal conversion, a leading 0x or 0X indicates hexadecimal conversion, and any other combination of leading characters indicates decimal conversion.
The function call atoq (str) is equivalent to strtoq (str, (char**)NULL, 10) .
x The converted value. __INT64_MAX or __INT64_MIN Indicates that the converted value would cause an overflow. 0 Indicates that the string starts with an unrecognized character or that the value for base is invalid. If the string starts with an unrecognized character, * endptr is set to nptr.
| Previous | Next | Contents | Index |