stdio reference

1. Standard Input/Output

Functions for console input and output operations.

Function	Description	Example
int printf(const char *format, ...)	Print formatted data to standard output (stdout).	printf("Age: %d", 25); // Output: Age: 25
int scanf(const char *format, ...)	Read formatted input from standard input (stdin).	scanf("%d", &age); // Reads integer into variable age
int putchar(int char)	Write a character to standard output.	putchar('A'); // Output: A
int getchar(void)	Read a character from standard input.	char c = getchar(); // Waits for user input

2. File Operations (Expanded)

Basic & Formatted I/O

Function	Description	Example
FILE *fopen(const char *filename, const char *mode)	Opens a file. Modes include "r" (read), "w" (write/overwrite), "a" (append), "rb" (read binary), etc.	FILE *fp = fopen("data.txt", "r"); // Opens file for reading
int fclose(FILE *stream)	Closes a file. Flushes buffers and releases the file pointer resource.	fclose(fp); // Closes the file pointer fp
int fprintf(FILE *stream, const char *format, ...)	Formatted write. Writes data to a file stream based on a format string.	fprintf(fp, "ID: %d\n", 42); // Writes "ID: 42" to file
int fscanf(FILE *stream, const char *format, ...)	Formatted read. Reads data from a file stream into variables according to a format.	int id; fscanf(fp, "%d", &id); // Reads an integer from file

Character & String I/O (Text Mode)

Function	Description	Example
char *fgets(char *str, int n, FILE *stream)	Read line. Reads a string from the file until a newline or n-1 characters are read.	char buf[100]; fgets(buf, 100, fp); // Reads a line into buf
int fputs(const char *str, FILE *stream)	Write string. Writes a string to the file (does not automatically append a newline).	fputs("Hello World\n", fp); // Writes string to file
int fgetc(FILE *stream)	Read character. Reads the next character from the stream (returns EOF on end).	int ch = fgetc(fp); // Reads a single char
int fputc(int char, FILE *stream)	Write character. Writes a single character to the stream.	fputc('A', fp); // Writes char 'A'

Binary / Block I/O

Function	Description	Example
size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream)	Block read. Reads an array of nmemb elements, each of size bytes, from the stream.	int nums[5]; fread(nums, sizeof(int), 5, fp); // Reads raw binary into array
size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream)	Block write. Writes an array of nmemb elements, each of size bytes, to the stream.	double d = 3.14; fwrite(&d, sizeof(double), 1, fp); // Writes binary data

File Positioning

Function	Description	Example
int fseek(FILE *stream, long int offset, int whence)	Move cursor. Moves the file pointer. whence: SEEK_SET (start), SEEK_CUR (current), SEEK_END (end).	fseek(fp, 0, SEEK_END); // Moves to end of file
long int ftell(FILE *stream)	Get position. Returns the current value (byte offset) of the file position indicator.	long pos = ftell(fp); // Gets current byte offset
void rewind(FILE *stream)	Reset cursor. Sets the file position indicator to the beginning of the file.	rewind(fp); // Same as fseek(fp, 0, SEEK_SET)

Status & Management

Function	Description	Example
int feof(FILE *stream)	Check End-Of-File. Returns a non-zero value if the End-Of-File indicator is set.	if(feof(fp)) break; // Stop loop if at EOF
int fflush(FILE *stream)	Flush buffer. Forces any buffered output data to be written to the physical file.	fflush(fp); // Ensures data is saved now
int remove(const char *filename)	Delete file. Deletes the file with the given name from the file system.	remove("data.txt"); // Deletes the file
int rename(const char *old, const char *new)	Rename file. Changes the name of a file from old to new.	rename("old.txt", "new.txt"); // Renames the file

3. String Formatting

Functions for formatting data into strings or parsing data from strings.

Function	Description	Example
int sprintf(char *str, const char *format, ...)	Write formatted data to a string buffer instead of stdout.	sprintf(buf, "Hi %s", "Bob"); // buf becomes "Hi Bob"
int sscanf(const char *str, const char *format, ...)	Read formatted data from a string.	sscanf("Year 2025", "%*s %d", &y); // Parses 2025 into variable y