File IO (Basic Knowledge)
Posted jasperzhao
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2 (1) 3 #include<stdio.h> 4 FILE * myFile = NULL; 5 myFile = fopen(“input_file.dat” , “r”); 6 /* r-> open for reading w-> writing a-> appending */ 7 If (myFile == NULL) 8 { 9 Printf(“error msg ”); 10 Exit(1); 11 } 12 char Buffer[500]; 13 int x; 14 fgets(Buffer,100,myFile); 15 sscanf(Buffer,”%d”,&x); 16 17 char x2[100]; 18 myFile = fopen(“output_file.dat”,”w”); 19 /* output_file.dat doesn’t exist: create it 20 Exist: overwrite */ 21 fprintf(myFile,”This is my output message! ”); 22 fscanf(myFile,”%c”,&x2); 23 24 fclose(myFile); 32 33 (2) 34 FILE *inFile = NULL; 35 FILE *outFile = NULL; 36 // Lab7 infile.dat outfile.dat 37 inFile = fopen(argv[1],”r”); 38 if(inFile == NULL) 39 { 40 Printf(“Error message! ”); 41 exit(1); 42 } 43 outFile = fopen(argv[2],”w”); 44 if(outFile == NULL) 45 { 46 Printf(“Error message! ”); 47 exit(1); 48 } 49 while( feof( inFile == 0 ) ) 50 { 51 If( fgets(Buffer,1000,inFile) ) 52 { 53 fprintf(outFile,”%s”,Buffer); 54 }//Read one line at a time 55 } 56 fclose(inFile); 57 fclose(outFile); 58 59 //OR: 60 //while ( fgets( Buffer,1000,inFile ) != NULL ) 61 //{ 62 // fprintf( outFile,”%s”,Buffer); 63 // } 64 65 (3) 66 FILE *inFile = NULL; 67 FILE *outFile = NULL; 68 char Buffer[100]; 69 // Lab7 infile.dat outfile.dat 70 inFile = fopen(argv[1],”rb”); // rb->read binary 71 if(inFile == NULL) 72 { 73 printf(“error Msg!”); 74 exit(1); 75 } 76 outFile = fopen(argv[2],”wb”); // wb->write binary 77 int x; double y; int z[10]; 78 fread( &x, sizeof(int), 1, inFile ); // data type of &x: void* 79 fread( &y, sizeof(double), 1, inFile); 80 fread ( z, sizeof(int), 10, inFile); 81 char A[20]; 82 fread(A, sizeof(char), 20, inFile); 83 fwrite(A, sizeof(char), 20, outFile); 84 fclose(inFile); 85 fclose(outFile);
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