Originální popis anglicky:
strtok, strtok_r - split string into tokens
Návod, kniha: POSIX Programmer's Manual
#include <string.h>
char *strtok(char *restrict
s1, const char
*restrict s2);
char *strtok_r(char *restrict s, const char *restrict
sep ,
char **restrict
lasts );
For
strtok(): The functionality described on this reference page is
aligned with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This volume of
IEEE Std 1003.1-2001 defers to the ISO C standard.
A sequence of calls to
strtok() breaks the string pointed to by
s1
into a sequence of tokens, each of which is delimited by a byte from the
string pointed to by
s2. The first call in the sequence has
s1
as its first argument, and is followed by calls with a null pointer as their
first argument. The separator string pointed to by
s2 may be different
from call to call.
The first call in the sequence searches the string pointed to by
s1 for
the first byte that is
not contained in the current separator string
pointed to by
s2. If no such byte is found, then there are no tokens in
the string pointed to by
s1 and
strtok() shall return a null
pointer. If such a byte is found, it is the start of the first token.
The
strtok() function then searches from there for a byte that
is
contained in the current separator string. If no such byte is found, the
current token extends to the end of the string pointed to by
s1, and
subsequent searches for a token shall return a null pointer. If such a byte is
found, it is overwritten by a null byte, which terminates the current token.
The
strtok() function saves a pointer to the following byte, from which
the next search for a token shall start.
Each subsequent call, with a null pointer as the value of the first argument,
starts searching from the saved pointer and behaves as described above.
The implementation shall behave as if no function defined in this volume of
IEEE Std 1003.1-2001 calls
strtok().
The
strtok() function need not be reentrant. A function that is not
required to be reentrant is not required to be thread-safe.
The
strtok_r() function 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 argument
lasts
points to a user-provided pointer which points to stored information necessary
for
strtok_r() to continue scanning the same string.
In the first call to
strtok_r(),
s points to a null-terminated
string,
sep to a null-terminated string of separator characters, and
the value pointed to by
lasts is ignored. The
strtok_r()
function shall return a pointer to the first character of the first token,
write a null character into
s immediately following the returned token,
and update the pointer to which
lasts points.
In subsequent calls,
s is a NULL pointer and
lasts shall be
unchanged from the previous call so that subsequent calls shall move through
the string
s, returning successive tokens until no tokens remain. The
separator string
sep may be different from call to call. When no token
remains in
s, a NULL pointer shall be returned.
Upon successful completion,
strtok() shall return a pointer to the first
byte of a token. Otherwise, if there is no token,
strtok() shall return
a null pointer.
The
strtok_r() function shall return a pointer to the token found, or a
NULL pointer when no token is found.
No errors are defined.
The following sections are informative.
The following example searches for tokens separated by <space>s.
#include <string.h>
...
char *token;
char *line = "LINE TO BE SEPARATED";
char *search = " ";
/* Token will point to "LINE". */
token = strtok(line, search);
/* Token will point to "TO". */
token = strtok(NULL, search);
The following example uses
strtok() to break a line into two character
strings separated by any combination of <space>s, <tab>s, or
<newline>s.
#include <string.h>
...
struct element {
char *key;
char *data;
};
...
char line[LINE_MAX];
char *key, *data;
...
key = strtok(line, " \n");
data = strtok(NULL, " \n");
...
The
strtok_r() function is thread-safe and stores its state in a
user-supplied buffer instead of possibly using a static data area that may be
overwritten by an unrelated call from another thread.
The
strtok() function searches for a separator string within a larger
string. It returns a pointer to the last substring between separator strings.
This function uses static storage to keep track of the current string position
between calls. The new function,
strtok_r(), takes an additional
argument,
lasts, to keep track of the current position in the string.
None.
The Base Definitions volume of IEEE Std 1003.1-2001,
<string.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
