1 / 14

Understanding File I/O in C Programming: fopen, fprintf, fscanf, and File Handling Techniques

This lecture by Munirul Haque covers essential concepts of file input/output (I/O) in C programming. It introduces the FILE structure from the stdio.h library and demonstrates how to use file pointers, or file handles, for reading and writing files. Key functions such as fopen, fprintf, and fscanf are explained with practical examples. The lecture also touches on character-level file operations and techniques for copying files. A solid grasp of these concepts is vital for effective file manipulation in C.

sheera
Télécharger la présentation

Understanding File I/O in C Programming: fopen, fprintf, fscanf, and File Handling Techniques

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. ETE 132Lecture 8 By Munirul Haque

  2. Topics • I/O, Streams, Files

  3. Files • The library stdio.h defines a structure called FILE. • You don’t need to know any of the details of how a FILE works, you just need to know how to point to them. • A pointer to a file is called a “file handle”.

  4. Writing to a File void main() { FILE *fp; /* pointer to a file */ /* open WRITEME.txt for reading */ fp = fopen("WRITEME.txt", “w"); /* do stuff with the file */ fprintf(fp,"This goes in the file"); /* close the file -- it’s a good habit */ fclose(fp); }

  5. fopen • The function fopen accepts a string corresponding to the name of the filename, and another string the says whether we want to open the file to • read ("r"), • Write ("w"), or • append ("a"). • If there is any error, fopen returns the pointer value NULL.

  6. Printf and Scanf with Files • Up to now, we’ve been using printf to print messages (to “standard output”), and scanf to receive input from the keyboard (from “standard input”). • These can be generalized to the functions fprintf and fscanf, which write to and read from a particular file.

  7. Printf and Scanf with Files • Given a file pointer fp, the statement: • fprintf(fp,"This goes in the file"); writes to the file handled by fp. • The statement: fscanf(fp,"%d",&intvar); reads an integer from the file.

  8. Other ways to read and write • There are more rudimentary ways to read from files and write to files. • Suppose that fp is a file pointer. • The function getc(fp) returns a single character read from the file. putc(c,fp); • writes the character c to the file.

  9. End of File • feof() returns non-zero if fp reaches end-of-file, otherwise zero. FILE *fp; while(!feof(fp)) ch = getc(ch);

  10. Reading from file • Reading character by character File *fp; char ch; fp = fopen(“myfile”, “r”); // open file to read while(!feof(fp)) { // read until end-of-file ch = getc(fp); printf(“%c”,ch); } fclose(fp); // close the file stream

  11. Writing to file • Writing character by character File *fp; char ch; fp = fopen(“myfile”, “w”); // open file to write while(1) { scanf(“%c”, &ch); if (ch == ‘\n’) break; // read until newline found putc(ch, fp); } fclose(fp);

  12. Copy file FILE *from, *to; char ch; from = fopen(“input.txt”, “r”); to = fopen(“output.txt”, “w”); while (!feof(from)) { ch = getc(from); putc (ch, to); } fclose(from); fclose(to);

  13. fscanf() • Read from file to specific variables double d; int i; char str[20], ch; FILE *fp; fscanf(fp, “%lf %d %s %c”, &d, &i, str, &ch); printf(“%lf %d %s %c”, d, i, str, c); fclose(fp);

  14. fprintf() • Write values from variables to file double d = 1234.5; int i = 10; char str[20] = “Hello”, ch = ‘Q’; FILE *fp; fprintf(fp, “%lf %d %s %c”, d, i, str, c); fclose(fp);

More Related