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char string[] = "Hello secure coding wiki!";
char *token;
token = strtok(string, ' ');
puts(token);
while ( token = strtok(NULL, ' ') ) {
puts(token);
}
/* string has been modified */
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In this example, the {{strtok()}} function is used to parse the first argument into space-delimited tokens; it will output each word from the string on a new line. However, after the while loop ends, string\[\] will have been modified to look like this: {{"Hello\0secure\0coding\0wiki\0"}}. Any further manipulation of {{string}} operating on the assumption that it is still whole will see only "Hello" instead of the expected string value. |
Compliant Solutions
One possible solution is to copy the string being tokenized into a temporary buffer which isn't referenced after the calls to strtok():
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char string[] = "Hello secure coding wiki!";
char buff[256];
char *token;
strncpy(buff, string);
token = strtok(buff, ' ');
printf("%s\n", token);
while ( token = strtok(NULL, ' ') ) {
printf("%s\n", token);
}
/* further string manipulation on string[] succeeds */
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References
Unix Man page strtok(3) Library functions which enter the namespace from linked-in libraries can have the same name as a #declare'd macro; in order to prevent such a naming conflict parenthesize the name of the library function when it is called:
