Question

新人求助！

/* print_it.c-This program prints a listing with line numbers! */
#include "stdlib.h"
#include "stdio.h"
void do_heading(char *filename);
int line = 0, page = 0;
int main ( int argv, char *argc[] )
{
char buffer[256];
FILE *fp;
if( argv < 2 )
{
fprintf(stderr, "\nproper usage is: " );
fprintf(stderr, "\n\nprint_it filename.ext\n" );
return(1);
}
if (( fp = fopen ( argc[1], "r" )) == NULL)
{
fprintf( stderr, "Error opening file, %&!", argc[1]);
return(1);
}

page = 0;
line = 1;
do_heading( argc[1] );

while( fgets( buffer, 256, fp ) != NULL )
{
if( line % 55 == 0 )
do_heading( argc[1] );

fprintf( stdprn, "%4d:\t%s", line++, buffer );
}

fprintf( stdprn, "\f" );
fclose(fp);
return 0;
}

void do_heading( char *filename )
{
page++;

if ( page > 1)
fprintf( stdprn, "page: %d, %s\n\n", page, filename );
}
这段代码对吗？ 还有为什么stdprn无法定义？

Answer 1

stdprn在标准的stdio.h中是没有定义的，你希望通过打印机输出，推荐的方法是自定义stdprn：

FILE *stdprn;
stdprn = fopen("PRN","wb");
fprintf(stdprn,"Hello, printer! \r\n");
fclose(stdprn);

希望能解决您的问题！