1 / 5

Text files

Text files. Text file contains ASCII-characters New line and end-of-file are special characters in a text file Ex. 1 This is a text<newline>It has two lines<newline><end-of-file> Examples of predifined text files stdin, stdout, stderr (these are file pointers)

anneke
Download Presentation

Text files

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Text files • Text file contains ASCII-characters • New line and end-of-file are special characters in a text file Ex. 1 • This is a text<newline>It has two lines<newline><end-of-file> • Examples of predifined text files stdin, stdout, stderr (these are file pointers) • stderr always associated with the screen • stdin, stdout might be re-directed to other text files TDBA66, vt-04, Lecture Ch9

  2. EOF EOF is defined in <stdio.h> and is returned from scanf() or fscanf() if end-of-file of the read file is detected Possible to check if EOF is read by e.g. for (status=scanf(”%d”, &num); status != EOF; status=scanf(”%d”, &num)) process(num); e.g. while (fscanf(infpt,”%d”, &num) != EOF) process(num); TDBA66, vt-04, Lecture Ch9

  3. Declare file pointers • Open a file for reading or writing • -check if opening was ok • Use it/them • Close them before ending program • Ex. 1 • FILE *inf, *outf; • if ((inf=fopen(”filname1.txt”,”r”)) == NULL){ • fprintf(stderr,”Error when opening filname1.txt”); • exit(-1); • } • if ((outf=fopen(”filname2.txt”,”w”))== NULL){ • fprintf(stderr,”Error when opening filname2.txt”); • exit(-2); • } Using text files TDBA66, vt-04, Lecture Ch9

  4. /* Makes a backup file. Repeatedly prompts for the name of a file to * back up until a name is provided that corresponds to an available * file. Then it prompts for the name of the backup file and creates * the file copy. */ #include <stdio.h> #define STRSIZ 80 intmain(void){ char in_name[STRSIZ], /* strings giving names */ out_name[STRSIZ]; /* of input and backup files */ FILE *inp, /* file pointers for input and */ *outp; /* backup files */ char ch; /* one character of input file */ int status; /* status of input operation */ /* Get the name of the file to back up and open the file for input*/ printf("Enter name of file you want to back up> "); for (scanf("%s", in_name); (inp = fopen(in_name, "r")) == NULL; scanf("%s", in_name)) { printf("Cannot open %s for input\n", in_name); printf("Re-enter file name> "); } TDBA66, vt-04, Lecture Ch9

  5. /*Get name to use for backup file and open file for output */ printf("Enter name for backup copy> "); for (scanf("%s", out_name); (outp = fopen(out_name, "w")) == NULL; scanf("%s", out_name)) { printf("Cannot open %s for output\n", out_name); printf("Re-enter file name> "); } /* Make backup copy one character at a time */ for (status = fscanf(inp, "%c", &ch); status != EOF; status = fscanf(inp, "%c", &ch)) fprintf(outp, "%c", ch); /* Close files and notify user of backup completion */ fclose(inp); fclose(outp); printf("Copied %s to %s.\n", in_name, out_name); return(0); } TDBA66, vt-04, Lecture Ch9

More Related