perror Function

Prints an error message to stderr.

Include

<stdio.h>

Prototype

void perror(const char * s);

Argument

s
string to print

Return Value

None.

Remarks

The string s is printed followed by a colon and a space. Then, an error message based on errno is printed followed by an newline.

Example

See the notes at the beginning of this chapter or section for information on using printf() or scanf() (and other functions reading and writing the stdin or stdout streams) in the example code.

#include <math.h>
#include <stdio.h>
#include <errno.h>

int main(void)
{
  double x,y;

  errno = 0;
  x = -2.0;
  y = acos (x);
  if (errno)
    perror("Error");
  printf("The arccosine of %f is %f\n", x, y);
}

Example Output

Error: Domain error
The arccosine of -2.000000 is nan