Week 12: File I/O in C Flashcards
What is the data type used to access files in C and what library is required?
FILE *
pointer
stdio.h is required
To open a file what command is used?
fopen()
format: fopen(“filename”, “mode”)
What are the following file modes?
r w a r+ w+ a+
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
What three files can be used with files?
stdout
stdin
stderr
What file function can you use to abruptly leave the file at any time?
exit()
exit(status);
What are the four ways to read and write files?
Format file I/O
Get and put a character
Get and put a line
Block read and write
Formatted file input and output is done through what functions?
fprintf()
fscanf()
What are the syntaxes of fprintf() and fscanf()
fprintf(FILE *fp, “string”);
fscanf(FILE *fp, “%d”, &address);
Get and put characters have what functions?
fgetc()
fputc()
What are the formats of fgetc() and fputc()
fgetc(FILE *fp);
fputc(int c, FILE *fp)
What are the functions used for getting and putting lines?
fgets()
fputs()
What is the format of fgets() and fputs()
char *fgets(char *s, int n, FILE *fp)
int fputs(char*s, FILE *fp);
What functions are used for binary reading and writing?
fwrite()
fread()
fread() and fwrite() have what formats?
int fwrite (void *buf, int size, int count, FILE *fp);
int fread (void *buf, int size, int count, FILE *fp);
What function closes a file?
fclose(FILE *fp);
What does flushing do?
Clear the buffer to force to the disk
What function is used to flush a file?
fflush(FILE *fp)
What function can be used to go to the beginning of the file?
void rewind(FILE *fp)
What function can be used to indicate where the current position in the file is?
long ftell(FILE *fp)
What function can be used to better control your position in a file?
fseek()
What is the format of fseek()
fseek(FILE *fp, long offset, int origin)
What do the following mean?
SEEK_SET
SEEK_CUR
SEEK_END
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
What does EOF mean and why can be be problematic
EOF = end of file
The problem is that the byte of data read may actually be
indistinguishable from EOF
What is the end of file function for binary vs text files?
Binary feof() Text: EOF
What are the functions for removing and renaming a file?
remove()
rename()
When will rename() return an error?
Oldname does not exist
Newname already exists
What function creates a temporary name?
tmpnam()
If fopen() fails what is returned?
NULL
if fopen() works what is returned?
A pointer to the file
