C atol() function

C atol() function - Convert a string to a long integer

The atol() function is used to convert a character string to a long value.

Syntax:

long int atol(const char *str)

Parameters:

Return value from atol()

• Returns a long value.

Example: atol() function

The following example shows the usage of atol() function.

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
 
int main(void)
{   
    char    *str = NULL;
    long    value = 0;
    // string value with leading and trailing white spaces.
    str = "  -7435 ";
    value = atol( str );
    printf( "Function: atol( \"%s\" ) = %d\n", str, value );

    // string value with an arbitrary decimal point.
    str = "732946.45";
    value = atol( str );
    printf( "Function: atol( \"%s\" ) = %d\n", str, value );

    // Another example with an overflow condition occurring.
    str = "234243820342342-422348";
    value = atol( str );
    printf( "Function: atol( \"%s\" ) = %d\n", str, value );
    if (errno == ERANGE)
    {
       printf("Overflow condition occurred.\n");
    }
}

Output:

Function: atol( "  -7435 " ) = -7435
Function: atol( "732946.45" ) = 732946
Function: atol( "234243820342342-422348" ) = 598985798

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