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Title: C Language File Handling Notes
Description: This is very Easy Notes For Student can Easily Learn
Description: This is very Easy Notes For Student can Easily Learn
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C Tutorial - File Handling
Files let you store data on secondary storage such as a hard disk so that your programs can later
retrieve that data again
...
Text files
Text files are used for storing character strings in a file
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#include
fopen takes 2 parameters which are the file
name and the open mode
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#include
txt","w");
return 0;
}
The above example will create a file called test
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The "w" means that the file is being opened for
writing and if the file does not exist then it will be created
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If the file exists then make
it blank
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If the file
exists then make it blank
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a+
Open for reading and appending and create the file if it does not exist
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fprintf is just like printf except that you
must use the file pointer as the first parameter
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h>
int main()
{
FILE *f;
f = fopen("test
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If you do not close a file then some of
the data might not be written to it
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#include
txt","w");
fprintf(f,"Hello");
fclose(f);
return 0;
}
The fgets command is used when reading from a text file
...
The 3 parameters for fgets are the buffer
variable, the size of the buffer and the file pointer
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h>
int main()
{
FILE *f;
char buf[100];
f = fopen("test
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When you open a data file you must add
the letter b to the open mode parameter of fopen
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h>
int main()
{
FILE *f;
f = fopen("test
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The first parameter of fwrite is a pointer to the variable that you want
to write to the file
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The third
parameter is the number of variables to be written
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#include
dat","wb");
buf = 100;
fwrite(&buf,sizeof(buf),1,f);
fclose(f);
return 0;
}
fread is used to read from a file and is the same as fwrite except that the data is read into the
variable instead of writing from it
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#include
dat","rb");
fread(&buf,sizeof(buf),1,f);
printf("%d\n",buf);
fclose(f);
return 0;
}
Data files using structures
You can read and write structures to data files in the same way as you do with any other data type
...
h>
struct
{
char name[100];
int age;
} p;
int main()
{
FILE *f;
strcpy(p
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age = 25;
f = fopen("test
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User is also asked for the line
number that is to be deleted
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The file is opened and all the data is transferred to another file except that one line the user specifies
to delete
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h>
int main() {
FILE *fp1, *fp2;
//consider 40 character string to store filename
char filename[40];
char c;
int del_line, temp = 1;
//asks user for file name
printf("Enter file name: ");
//receives file name from user and stores in 'filename'
scanf("%s", filename);
//open file in read mode
fp1 = fopen(filename, "r");
c = getc(fp1);
//until the last character of file is obtained
while (c != EOF)
{
printf("%c", c);
//print current character and read next character
c = getc(fp1);
}
//rewind
rewind(fp1);
printf(" \n Enter line number of the line to be deleted:");
//accept number from user
...
c", "w");
c = getc(fp1);
while (c != EOF) {
c = getc(fp1);
if (c == '\n')
temp++;
//except the line to be deleted
if (temp != del_line)
{
//copy all lines in file copy
...
fclose(fp1);
fclose(fp2);
//remove original file
remove(filename);
//rename the file copy
...
c", filename);
printf("\n The contents of file after being modified are as follows:\n");
fp1 = fopen(filename, "r");
c = getc(fp1);
while (c != EOF) {
printf("%c", c);
c = getc(fp1);
}
fclose(fp1);
return 0;
}
Output:
Enter file name:abc
...
Hello
how are you?
I am fine
hope the same
Enter line number of the line to be deleted:4
The contents of file after being modified are as follows:
hi
...
Entered file name is stored in
a char array 'filename'
...
Character 'c' is used
to read characters from the file and print them to the output
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The file pointer is rewinded back and all the lines of the file except for the line to be
deleted are copied into another file "copy
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Now "copy
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The
original file is opened in read mode and the modified contents of the file are displayed on the screen
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h>
int main(void) {
FILE *fp1, *fp2;
//'filename'is a 40 character string to store filename
char filename[40];
char c;
int del_line, temp = 1;
//asks user for file name
printf("Enter file name: ");
//receives file name from user and stores in 'filename'
scanf("%s", filename);
fp1 = fopen(filename, "r");
//open file in read mode
c = getc(fp1);
//print the contents of file
...
printf(" Enter line number to be deleted and replaced");
scanf("%d", &del_line);
//take fp1 to start point
...
c in write mode
fp2 = fopen("copy
...
c", filename);
fp1 = fopen(filename, "r");
//reads the character from file
c = getc(fp1);
//until last character of file is encountered
while (c != EOF){
printf("%c", c);
//all characters are printed
c = getc(fp1);
}
//close the file pointer
fclose(fp1);
return 0;
}
Output:
Enter file name:abc
...
hello
how are you?
hope the same
Enter line number of the line to be deleted and replaced:4
Enter new text: sayonara see you soon
hi
...
The File by name entered by user is
opened in read mode
...
Next the data to
be replaced is asked
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c"
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New data is stored in
its place and remaining lines of the original file are also transferred
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Both the file pointers are closed and the original file
is again opened in read mode and the contents of the original file is printed as output
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#include
sample_chr = getc(fp);
}
fclose(fp); //close file
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txt
There are 4 lines in abc
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A file by the given name is opened in
read-mode using a File pointer 'fp'
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If a new line character(' ') is encountered, the integer variable
'no_lines' is incremented
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This process is continued until the last character of the file(EOF) is
encountered
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Title: C Language File Handling Notes
Description: This is very Easy Notes For Student can Easily Learn
Description: This is very Easy Notes For Student can Easily Learn