Week 12: File I/O in C

Question 1

What is the data type used to access files in C and what library is required?

Answer 1

FILE *

pointer

stdio.h is required

Question 2

To open a file what command is used?

Answer 2

fopen()

format: fopen(“filename”, “mode”)

Question 3

What are the following file modes?

r
w
a
r+
w+
a+

Answer 3

r : open the file for reading (NULL if it doesn’t exist)

w : create for writing. destroy old if file exists

a : open for writing. create if not there. start at the end-of-file

r+ : open for update (r/w). create if not there. start at the beginning.

w+ : create for r/w. destroy old if there

a+ : open for r/w. create if not there. start at the end-of-file

Question 4

What three files can be used with files?

Answer 4

stdout

stdin

stderr

Question 5

What file function can you use to abruptly leave the file at any time?

Answer 5

exit()

exit(status);

Question 6

What are the four ways to read and write files?

Answer 6

Format file I/O

Get and put a character

Get and put a line

Block read and write

Question 7

Formatted file input and output is done through what functions?

Answer 7

fprintf()

fscanf()

Question 8

What are the syntaxes of fprintf() and fscanf()

Answer 8

fprintf(FILE *fp, “string”);

fscanf(FILE *fp, “%d”, &address);

Question 9

Get and put characters have what functions?

Answer 9

fgetc()

fputc()

Question 10

What are the formats of fgetc() and fputc()

Answer 10

fgetc(FILE *fp);

fputc(int c, FILE *fp)

Question 11

What are the functions used for getting and putting lines?

Answer 11

fgets()

fputs()

Question 12

What is the format of fgets() and fputs()

Answer 12

char *fgets(char *s, int n, FILE *fp)

int fputs(char*s, FILE *fp);

Question 13

What functions are used for binary reading and writing?

Answer 13

fwrite()

fread()

Question 14

fread() and fwrite() have what formats?

Answer 14

int fwrite (void *buf, int size, int count, FILE *fp);

int fread (void *buf, int size, int count, FILE *fp);

Question 15

What function closes a file?

Answer 15

fclose(FILE *fp);

Question 16

What does flushing do?

Answer 16

Clear the buffer to force to the disk

Question 17

What function is used to flush a file?

Answer 17

fflush(FILE *fp)

Question 18

What function can be used to go to the beginning of the file?

Answer 18

void rewind(FILE *fp)

Question 19

What function can be used to indicate where the current position in the file is?

Answer 19

long ftell(FILE *fp)

Question 20

What function can be used to better control your position in a file?

Answer 20

fseek()

Question 21

What is the format of fseek()

Answer 21

fseek(FILE *fp, long offset, int origin)

Question 22

What do the following mean?

SEEK_SET

SEEK_CUR

SEEK_END

Answer 22

SEEK_SET
move the indicator offset bytes from the beginning

SEEK_CUR
move the indicator offset bytes from its current position

SEEK_END
move the indicator offset bytes from the end

Question 23

What does EOF mean and why can be be problematic

Answer 23

EOF = end of file
The problem is that the byte of data read may actually be
indistinguishable from EOF

Question 24

What is the end of file function for binary vs text files?

Answer 24

Binary feof()
Text: EOF

Question 25

What are the functions for removing and renaming a file?

Answer 25

remove()

rename()

Question 26

When will rename() return an error?

Answer 26

Oldname does not exist

Newname already exists

Question 27

What function creates a temporary name?

Answer 27

tmpnam()

Question 28

If fopen() fails what is returned?

Answer 28

NULL

Question 29

if fopen() works what is returned?

Answer 29

A pointer to the file