-
-
Notifications
You must be signed in to change notification settings - Fork 2
str_tok.3
str_tok - extract tokens from strings
#include <string.h>
char *str_tok(char *str, const char *delim);
The str_tok() function breaks a string into a sequence of zero or more nonempty tokens. On the first call to str_tok(), the string to be parsed should be specified in str. In each subsequent call that should parse the same string, str must be NULL.
The delim argument specifies a set of bytes 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 str_tok() returns a pointer to a null-terminated string containing the next token. This string does not include the delimiting byte. If no more tokens are found, str_tok() returns NULL.
A sequence of calls to str_tok() that operate on the same string maintains a pointer that determines the point from which to start searching for the next token. The first call to str_tok() sets this pointer to point to the first byte of the string. The start of the next token is determined by scanning forward for the next nondelimiter byte in str. If such a byte is found, it is taken as the start of the next token. If no such byte is found, then there are no more tokens, and str_tok() returns NULL. (A string that is empty or that contains only delimiters will thus cause str_tok() to return NULL on the first call.)
The end of each token is found by scanning forward until either the next delimiter byte is found or until the terminating null byte ('\0') is encountered. If a delimiter byte is found, it is overwritten with a null byte to terminate the current token, and str_tok() saves a pointer to the following byte; that pointer will be used as the starting point when searching for the next token. In this case, str_tok() returns a pointer to the start of the found token.
From the above description, it follows that a sequence of two or more contiguous delimiter bytes in the parsed string is considered to be a single delimiter, and that delimiter bytes at the start or end of the string are ignored. Put another way: the tokens returned by str_tok() are always nonempty strings. Thus, for example, given the string "aaa;;bbb,", successive calls to str_tok() that specify the delimiter string ";," would return the strings "aaa" and "bbb", and then a null pointer.
The str_tok() function returns a pointer to the next token, or NULL if there are no more tokens.
Be cautious when using these functions. If you do use them, note that:
-
This function modify its first argument.
-
This function cannot be used on constant strings.
-
The identity of the delimiting byte is lost.
-
The str_tok() function uses a static buffer while parsing, so it's not thread safe.
index(3) memchr(3) rindex(3) strchr(3) string(3) strpbrk(3) strsep(3) strspn(3) strstr(3) wcstok(3)