cppreference.com > Standard C String and Character > atol atol Syntax:
      #include <stdlib.h>
      long atol( const char *str );
The function atol() converts str into a long, then returns that value. atol() will read from str until it finds any character that should not be in a long. The resulting truncated value is then converted and returned. For example,
       x = atol( "1024.0001" );
results in x being set to 1024L. Related topics: atof atoi (Standard C I/O) sprintf strtol