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In this example, the strtok() function is used to parse the first argument into colon-delimited tokens; it outputs each word from the string on a new line. Assume that PATH is "/usr/bin:/usr/sbin:/sbin".

char *token;
char *path = getenv("PATH");

token = strtok(path, ":");
puts(token);

while (token = strtok(0, ":")) {
  puts(token);
}

printf("PATH: %s\n", path);
/* PATH is now just "/usr/bin" */

However, after After the loop ends, path will have been modified to look like this is modified as follows: "/usr/bin\0/bin\0/usr/sbin\0/sbin\0". This is an issue on several levels. The because the local path variable becomes /usr/bin. Even worse, and because the environment variable PATH has been unintentionally changed, which could cause have unintended resultsconsequences.

Compliant Solution

In this solution the string being tokenized is copied into a temporary buffer which is not referenced after the calls to strtok():

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