檔案開關實例

1. 範例：從命令外加參數指定檔案，測試檔案是否存在。

   [dywang@deyu zzz]$ vim fileio1.c
   [dywang@deyu zzz]$ cat fileio1.c
   #include <stdio.h>
   
   int main( int argc, char *argv[] ) {
   	FILE *fp;
   	
   	fp = fopen( argv[1], "r" );
   	if( fp != NULL) {
   		printf("File %s exist.\n", argv[1]);
   	} 
   	else {
   		printf("File %s does not exist.\n", argv[1]);
   	}
   	fclose(fp);
   
   	return 0;
   }
   

2. 編譯

   [dywang@deyu zzz]$ gcc -o fileio1 fileio1.c
   

3. 執行結果：命令外加參數指定要開啟的檔案名， fileio.txt 檔案存在， fileio.aaa 不存在。

   [dywang@deyu zzz]$ ./fileio1 fileio.txt
   File fileio.txt exist.
   [dywang@deyu zzz]$ ./fileio1 fileio.aaa
   File fileio.aaa does not exist.