What is the perror function used for in C programming?

Answer 1

The perror() function is used to print a user-defined error message to stderr. Consider the following:

Example:

#include

int main ()

{

FILE * pFile;

pFile=fopen ("missing.txt","rb");

if (pFile==NULL)

perror ("missing.txt");

else

fclose (pFile);

return 0;

}

Possible Output:

missing.txt: No such file or directory

We can achieve the exact same effect with a more verbose fprintf() statement, such that the following are equivalent:

perror ("Error");

fprintf (stderr, "Error: %s\n", strerror (errno));

The following are also equivalent:

perror (NULL);

fprintf (stderr, strerror (errno));

We typically use fprintf() statement when we need to print messages other than those provided by strerror and/or wish to redirect the output to a device other than stderr. But for all error messages based upon the thread-local errno, perror is more concise and reduces the chances of introducing errors through typos (such as accidently redirecting errors to stdout instead of stderr).