Formatted input and output functions in C

The following are built-in functions available in C language which can be used to perform formatted input output operations.

Formatted input functions in C:
int fscanf(FILE *stream, const char *format, ...)
Performs input format conversion.  It reads the input from the stream and does format conversion.  Then, it will assign those converted values to the subsequent arguments of format correspondingly.  And it returns the number of inputs matched and got assigned with values successfully.

int scanf(const char *format, ...)
scanf() is equivalent to fscanf(stdin, ...)

int sscanf(char *str, const char *format)
sscanf() is identical to sscanf() except that the inputs are taken from the string str.

scanf fscanf sscanf example in C

  #include <stdio.h>
  int main() {
        FILE *fp;
        int i, age[3], rollno[3];
        char name[3][32], str[128] = "13:103:Ram";
        fp = fopen("input.txt", "r");

        /* input data for student 1 from user */
        printf("Enter age rollno and name for student 1:\n");
        scanf("%d%d%s", &age[0], &rollno[0], name[0]);

        printf("Reading age, rollno and name from file(input.txt)..\n");
        /* input data for student 2 from file */
        fscanf(fp, "%d%d%s", &age[1], &rollno[1], name[1]);

        printf("Reading age, rollno and name from string..\n");
        /* input data for student 3 from string */
        sscanf(str, "%d:%d:%s", &age[2], &rollno[2], name[2]);
                printf("          Age  Rollno name\n");

        /* print the result */
        for (i = 0; i < 3; i++) {
                printf("Student %d: %d    %d    %s\n",
                                i, age[i], rollno[i], name[i]);
        }
        fclose(fp);
        return 0;
  }

  Output:
  jp@jp-VirtualBox:~/$ cat input.txt
  10 102 Raj

  jp@jp-VirtualBox:~/$ ./a.out
  Enter age rollno and name for student 1:
  11 101 Tom
  Reading age, rollno and name from file(input.txt)..
  Reading age, rollno and name from string..
                 Age  Rollno name
  Student 0: 11    101    Tom
  Student 1: 10    102    Raj
  Student 2: 13    103    Ram

Formatted output functions in C:
int fprintf(FILE *stream, const char *format, . . .)
Performs formatted output conversion and writes the output to stream.  Return value is the number of characters printed (excludes '\0').

int printf(const char *format, . . .)
printf() is identical to fprintf(stdout, . . .)

int sprintf(char *str, const char *format, . . .)
sprintf() is similar to printf() except that the output is written into the string str.

int vfprintf(FILE *stream, const char *format, va_list arg)
vfprintf() is equivalent to fprintf() except that the variable argument is replaced by arg.

int vprintf(const char *format, va_list arg)
vprintf() is equivalent to printf() except that the variable argument is replaced by arg.

int vsprintf(char *str, const char *format, va_list  arg)
vsprintf() is equivalent to sprintf() except that the variable argument is replaced by arg.

printf fprintf sprintf example in C

  #include <stdio.h>
  int main() {
        FILE *fp;
        int rollno = 101, age = 10;
        char name[32] = "Ram", str[128];
        fp = fopen("input.txt", "w");

        /* printing rollno, age and name in stdout */
        printf("Writing output to stdout:\n");
        printf("Roll no: %d\n", rollno);
        printf("age    : %d\n", age);
        printf("Name   : %s\n", name);

        /* printing rollno, age and name in a file */
        printf("\nWriting rollno, age, name to file(input.txt)\n");
        fprintf(fp, "Roll no: %d\nage    : %d\nName   : %s\n",
                        rollno, age, name);

        /* printing rollno, age and name in a string */
        printf("Writing rollno, age, name to string(str)\n");
        sprintf(str, "Roll no: %d\nage    : %d\nName   : %s\n",
                        rollno, age, name);
        printf("\nContents in string str:\n%s\n", str);
        fcl