Standard Input / Output

Standard output

putchar

int putchar(int ch)

• Writes a character to standard output.
• Returns EOF on error.

puts

int puts(char *line)

• Writes a string to standard output.
• Automatically adds a newline character.
• Returns EOF on error.

printf

int printf(char *format, ...)

• Returns the number of characters printed.

Examples

#include <stdio.h> 
... 
printf("Hello, world!\n");

#include <stdio.h> 
... 
char str_value[100];
int int_value;
float float_value;
double double_value;
...
printf("String: %s\n", str_value);
printf("Integer: %d\n", int_value);
printf("Float, 2 decimal places: %.2f\n", float_value);
printf("Double, 5 decimal places: %.5f\n",
double_value);

Standard input

getchar

int getchar()

• Reads a character from standard input.
  
• Returns EOF on end-of-file.
  

gets

char *gets(char *line, int maxline)

• Reads the entire current line, including the newline character.
• Returns at most maxline-1 characters plus an end-of-string character ('{content}').
  
• Returns NULL on end-of-file or error.

scanf

int scanf(char *format, ...)

• Returns the number of input items successfully parsed.
• It can be called multiple times with different formatting options until the item is successfully parsed.

Examples

#include <stdio.h> 
... 
char name[100];
int age;
float short_pi;
double long_pi;

scanf("%s", name);        /* Read a string */
scanf("%d", &age);        /* Read an integer */
scanf("%f", &short_pi);   /* Read a float */
scanf("%lf", &long_pi);   /* Read a double */