C - Files

Question 1

fK1 stdin, stdout, stderr

Answer 1

global constant pointers,
standard streams for input, output and error output.

Question 2

K2 FILE *

Answer 2

https://www.tutorialspoint.com/cprogramming/c_file_io.htm

FILE *fp; //declare file
object containing information to control a stream.

can read, write to, appand to files. or close them.

fclose returns 0 on success

Question 3

K3 enum

Answer 3

https://www.w3schools.com/c/c_enums.php
special type that represents a group of constants.
//create enum
enum Level {
LOW,
MEDIUM,
HIGH
};

//create variable of enum
enum Level myVar;

//assigned value must of of LOW, MEDIUM, or HIGH. match enum items
enum Level myVar = MEDIUM;

by default, first item assigned value 0. second 1. third 2.

enum Level {
LOW = 25,
MEDIUM = 50,
HIGH = 75
};

Question 4

K4 struct

Answer 4

https://www.w3schools.com/c/c_structs.php

way to group related variables into one place. can contain different data types (int, float, char).

can’t just assign strings to elements in structures normally. use strcpy() instead.

strcpy(s1.myString, “some text”);

Question 5

K5 chain of responsibility

Answer 5

behavioral design pattern, passing requests along a chain of handlers. handlers either process the request or pass it to the next handler

Question 6

F1 fopen

Answer 6

FILE *fopen( const char * “filename.txt”, “w+” );
r - open text file
w - open text file to write on. create new file if doesn’t exist. writes from beginning of file.
a - open and append.
r+ open for read and write
w+ open for read and write, truncates file to zero length.
a+ open for read and write, write from beginning but can only append.

Question 7

F2 fclose

Answer 7

int fclose( FILE *fp );

closes file. return 0 on success or EOF failiure. flushes pending data in the buffer, closes the file, releases memory.

Question 8

F3 fread

Answer 8

binary input,

size_t fread(void *ptr, size_t size_of_elements, size_t number_of_elements, FILE *a_file);

Question 9

F4 fwrite

Answer 9

binary output

size_t fwrite(const void *ptr, size_t size_of_elements, size_t number_of_elements, FILE *a_file);

Question 10

F5 fseek

Answer 10

fseek( fp, 7, SEEK_SET ); //sets file position of fp(stream) to 7(given offset).

Question 11

F6 ftell

Answer 11

returns the current file position of the given stream.

fp = fopen(“file.txt”, “r”);
fseek(fp, 0, SEEK_END);
len = ftell(fp);

printf(“Total size of file.txt = %d bytes\n”, len); //Total size of file.txt = 26 bytes

https://www.tutorialspoint.com/c_standard_library/c_function_ftell.htm

Question 12

F7 fflush

Answer 12

https://www.tutorialspoint.com/c_standard_library/c_function_fflush.htm

flushes the output buffer of a stream

fprintf(stdout, “This output will go into buff\n”);
fflush( stdout );

fprintf(stdout, “and this will appear when programm\n”);
sleep(5);

Question 13

F8 fgets

Answer 13

https://www.tutorialspoint.com/c_standard_library/c_function_fgets.htm
char *fgets(char *str, int n, FILE *stream)

reads a line from the specified stream and stores it into the string pointed to by str

if( fgets (str, 60, fp)!=NULL ) {
/* writing content to stdout */
puts(str);
}

Question 14

F9 fgetc

Answer 14

https://www.tutorialspoint.com/c_standard_library/c_function_fgetc.htm
gets the next (unsigned char) character from the specified stream and advances the stream’s indicator.

get character and advance pointer

Question 15

F10 fputs

Answer 15

https://www.tutorialspoint.com/c_standard_library/c_function_puts.htm
int puts(const char *str)

write string to stdout, excluding NULL character

Question 16

F11 fputc

Answer 16

https://www.tutorialspoint.com/c_standard_library/c_function_fputc.htm
int fputc(int char, FILE *stream)
writes a character (char) to the specified stream and advances the position indicator for the stream

FILE *fp;
int ch;
fp = fopen(“file.txt”, “w+”);
for( ch = 33 ; ch <= 100; ch++ ) {
fputc(ch, fp);
}

put character and advance pointer

Question 17

Q1 what is a file in linux?

Answer 17

container used for storing data.

Question 18

Q2 what is the difference between fopen() and open()?
what is the difference between what they return?

Answer 18

open(): low-level cll
fopen(): calls the open() function in the background and returns a Filepointer directly.