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#include <stdlib.h>

int atoi (
  const unsigned char *string);   /* string to convert */

The atoi function converts string into an integer value. The input string must be a sequence of characters that can be interpreted as an integer. This function stops processing characters from string at the first one it cannot recognize as part of the number.

The string passed to atoi must have the following format:

〚whitespace〛〚{+|-}〛 digits



May be any number of space(' '), tab ('\t'), newline ('\n'), or carriage return ('\r') characters.


May be one or more decimal digits.
Return Value

The atoi function returns the integer value that is produced by interpreting the characters in string as a number.

If no conversion could be performed, 0 is returned.

See Also

atof, atol

#include <stdlib.h>
#include <stdio.h> /* for printf */

void tst_atoi (void) {
  int i;
  char s [] = "12345";

  i = atoi (s);
  printf ("ATOI(%s) = %d\n", s, i);
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