strtok和strtok_r函数

NAME

       strtok, strtok_r - extract tokens from strings

SYNOPSIS

       #include <string.h>       char *strtok(char *str, const char *delim);       char *strtok_r(char *str, const char *delim, char **saveptr);   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):       strtok_r(): _SVID_SOURCE || _BSD_SOURCE || _POSIX_C_SOURCE >= 1 ||       _XOPEN_SOURCE || _POSIX_SOURCE

DESCRIPTION

       The strtok() function parses a string into a sequence  of  tokens.   On       the  first call to strtok() the string to be parsed should be specified       in str.  In each subsequent call that should parse the same string, str       should be NULL.       The  delim  argument  specifies  a  set  of characters that delimit the       tokens in the parsed string.  The caller may specify different  strings       in delim in successive calls that parse the same string.       Each  call  to  strtok()  returns a pointer to a null-terminated string       containing the next token.  This string does not include the delimiting       character.  If no more tokens are found, strtok() returns NULL.       A sequence of two or more contiguous delimiter characters in the parsed       string is considered to be a single delimiter.  Delimiter characters at       the  start  or  end  of  the  string are ignored.  Put another way: the       tokens returned by strtok() are always nonempty strings.       The strtok_r() function is a reentrant version strtok().   The  saveptr       argument  is  a pointer to a char * variable that is used internally by       strtok_r() in order to maintain context between successive  calls  that       parse the same string.       On  the  first call to strtok_r(), str should point to the string to be       parsed, and the value of saveptr is ignored.  In subsequent calls,  str       should  be  NULL,  and  saveptr  should be unchanged since the previous       call.       Different strings may be parsed concurrently using sequences  of  calls       to strtok_r() that specify different saveptr arguments.

RETURN VALUE

       The  strtok()  and  strtok_r()  functions  return a pointer to the next       token, or NULL if there are no more tokens.

CONFORMING TO

       strtok()              SVr4, POSIX.1-2001, 4.3BSD, C89, C99.       strtok_r()              POSIX.1-2001.

BUGS

       Be cautious when using these functions.  If you do use them, note that:       * These functions modify their first argument.       * These functions cannot be used on constant strings.       * The identity of the delimiting character is lost.       * The strtok() function uses a static buffer while parsing, so it's not         thread safe.  Use strtok_r() if this matters to you.

EXAMPLE

       The program below uses nested loops that employ strtok_r() to  break  a       string  into  a  two-level hierarchy of tokens.  The first command-line       argument specifies the  string  to  be  parsed.   The  second  argument       specifies the delimiter character(s) to be used to separate that string       into "major"  tokens.   The  third  argument  specifies  the  delimiter       character(s)  to be used to separate the "major" tokens into subtokens.       An example of the output produced by this program is the following:           $ ./a.out 'a/bbb///cc;xxx:yyy:' ':;' '/'           1: a/bbb///cc                    --> a                    --> bbb                    --> cc           2: xxx                    --> xxx           3: yyy                    --> yyy   Program source  
 #include <stdio.h>       #include <stdlib.h>       #include <string.h>       int       main(int argc, char *argv[])       {           char *str1, *str2, *token, *subtoken;           char *saveptr1, *saveptr2;           int j;           if (argc != 4) {               fprintf(stderr, "Usage: %s string delim subdelim\n",                       argv[0]);               exit(EXIT_FAILURE);           }           for (j = 1, str1 = argv[1]; ; j++, str1 = NULL) {               token = strtok_r(str1, argv[2], &saveptr1);               if (token == NULL)                   break;               printf("%d: %s\n", j, token);               for (str2 = token; ; str2 = NULL) {                   subtoken = strtok_r(str2, argv[3], &saveptr2);                   if (subtoken == NULL)                       break;                   printf(" --> %s\n", subtoken);               }           }           exit(EXIT_SUCCESS);       } /* main */

SEE ALSO

       index(3),  memchr(3),  rindex(3),  strchr(3),  strpbrk(3),   strsep(3),       strspn(3), strstr(3), wcstok(3)

COLOPHON

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