File Input and Output
In this lab you will gain experience with both basic file input and output involving characters and strings as well as binary objects.
The program readfiles.c has some examples for how to handle opening a file for reading, reading until the end of the file and closing files properly.
Basic File Utilities
Catching File Errors
Download, review, and compile the
fopen-test.cfrom the reading.
- Run the program, trying to generate as many different error messages as you can.
fprintfcall within the
(stream == NULL)test to use a call to
perrorinstead. Recompile and run the program to generate the associated error. How does the output change?
The reading advised you that the
argctest should not be changed to a
perror. Make that change anyhow, then recompile and run the program to generate the associated error. What output do you get? Explain why that output is sensible in this context.
Counting characters, words, and lines:
Like the command line utility,
wc, write a small program called
getcto count all the characters in a file whose name is given as a command line argument. The program simply prints how many letters, spaces, newlines, and other characters there are in the file.
- Your program should report human readable errors and exit if the file cannot be opened for reading. (If you use example code from the reading, be sure you cite it appropriately.)
In order to to test for
EOFcorrectly, the textbooks and manual pages remind us that
int, not a
To distinguish between the end of file condition and a read
error, your program should use the function
- If a read error occurred, your program should report a human-readable message and exit.
- Remember to close the file when you are done reading from it.
mywc.cprogram so that it will also count and print how many words there are in the specified file.
- In this program, consider a word to be any consecutive sequence of letters separated by white space. Thus, you can count a word by identifing an initial letter and then skipping through any subsequent letters until you read a whitespace character. You'd start a new word again once you read a non-space character.
<ctype.h>should prove helpful.
mywc.cprogram so that it will also count and print how many lines there are in the specified file.
Write a small C program called
mycat.cthat reads all the text files whose names are given on the command line and prints their contents to
You will likely find the C library functions
puts) useful. Recall that, in contrast with
NULLwhen it encounters the end of the file or an error.
- If any file cannot be opened for reading, your program should report human readable error and continue with the next file. (If you use example code, be sure you cite it appropriately.)
- If a read error occurred, your program should report a human readable message to the standard error stream and continue with the next file.
- Remember to close each file when you are done (even if there was a read error).
- You will likely find the C library functions
Write a program that instructs the robot to take a picture and then
structwith the picture data to a file using
Write a companion program that uses
freadto read the binary data for a picture
structand then uses
MyroCheader to display the picture.