Looking for a Tutor Near You?

Post Learning Requirement »
x

Choose Country Code

x

Direction

x

Ask a Question

x

x
x
For better view click here
x
Hire a Tutor
DISCOVER

Note On File Handling Using C

Loading...

Published in: C / C++
548 Views

Accessing file and basic operations like read, write, append, open and close.

Prantik S / Kolkata

11 years of teaching experience

Qualification: MCA (Jaipur National University - [JNU], Jaipur - 2017)

Teaches: Basic Computer, Computer for official job, MS Office, School Level Computer, ICT Training, Computer Science, Information Practice, IT & Computer Subjects, BCA Tuition, IT, Computer, C / C++, C# (C Sharp), Java And J2EE, Python Programming, Visual Basic, BCA Subjects, Hardware Training, Networking, Java Script

Contact this Tutor
  1. Working with files using C. Accessing Files An external file can be opened, read from, and written to in a C program. For these operations, C includes the FILE type for defining a file stream. The file stream keeps track of where reading and writing last occurred. The stdio.h library includes file handling functions: FILE Typedef for defining a file pointer. fopen(filename, mode) Returns a FILE pointer to file filename which is opened using mode. If a file cannot be opened, NULL is returned. Mode options are: - r open for reading (file must exist) - w open for writing (file need not exist) - a open for append (file need not exist) - r+ open for reading and writing from beginning - w+ open for reading and writing, overwriting file - a+ open for reading and writing, appending to file Closing a file when you are done using it is a good programming practice. fclose(fp) Closes file opened with FILE fp, returning 0 if close was successful. EOF (end of file) is returned if there is an error in closing. The following program opens a file for writing and then closes it: #include int main() { FILE *fptr,• fptr = fopen("myfile.txt", "w"); if (fptr NULL) { printf("Error opening file. return -1 ;
  2. fclose(fptr); return 0; When a string literal is used to specify a filename, the escape sequence \\ indicates a single backslash. In this program, if there is an error when opening the file, a -1 error code is returned to the system. Error handling is explained in a future lesson. Reading from a File. The stdio.h library also includes functions for reading from an open file. A file can be read one character at a time or an entire string can be read into a character buffer, which is typically a char array used for temporary storage. fgetc(fp) Returns the next character from the file pointed to by fp. If the end of the file has been reached, then EOF is returned. fgets(buff, n, fp) Reads n-l characters from the file pointed to by fp and stores the string in buff. A NULL character '\0' is appended as the last character in buff. If fgets encounters a newline character or the end of file before n-l characters is reached, then only the characters up to that point are stored in buff. fscanf(fp, conversion_specifiers, vars) Reads characters from the file pointed to by fp and assigns input to a list of variable pointers vars using conversion_specifiers. As with scanf, fscanf stops reading a string when a space or newline is encountered. The following program demonstrates reading from a file: Try this Yourself #include int main() { FILE *fptr,• int c, stock; char buffer[200], item[1 0]; float price; /* myfile.txt: Inventory\nl 00 Widget 0.29\nEnd of List */ fptr = fopen("myfile.txt", "r");
  3. fgets(buffer, 20, fptr); /* read a line */ printf("%s\n", buffer); fscanf(fptr, "%d%s%f", &stock, item, &price); /* read data */ printf("%d %s 0/04.2f\n", stock, item, price); while ((c = getc(fptr)) != EOF) /* read the rest of the file */ printf("%c", c); fclose(fptr); return 0; Task: Print the output The gets() function reads up until the newline. fscanf() reads data according to conversion specifiers. And then the while loop reads one character at a time until the end of file. Checking for a problem when opening the file (a NULL pointer) was left out to shorten the example. Writing to a File The stdio.h library also includes functions for writing to a file. When writing to a file, newline characters I\nl must be explicitly added. fputc(char, fp) Writes character char to the file pointed to by fp. fputs(str, fp) Writes string str to the file pointed to by fp. fprintf(fp, str, vars) Prints string str to the file pointed to by fp. str can optionally include format specifiers and a list of variables vars. The following program demonstrates writing to a file: #include int main() { FILE *fptr,• char filename[50]; char c; printf("Enter the filename of the file to create: ");
  4. gets(filename); fptr = fopen(filename, "w"); /* write to file */ fprintf(fptr, "Inventory\n"); fprintf(fptr, "0/0d %s 0/0f\n", 1 00, "Widget", 0.29); fputs("End of List", fptr); fclose(fptr); /* read the file contents */ fptr = fopen(filename, "r"); while ((c = getc(fptr)) != EOF) printf("%c", c); fclose(fptr); return 0; The "w" argument defines "writing mode" for the fopen function.

Need a Tutor or Coaching Class?

Post an enquiry and get instant responses from qualified and experienced tutors.

Post Requirement

Related Study Notes

Upload Study Notes

If you have your own Study Notes which you think can benefit others, please upload on LearnPick. For each approved Study Note you will get 100 Credit Points and 100 Activity Score which will increase your profile visibility.

Upload Now
Home > Study Notes > Note On File Handling Using C