Input files to test project 2. Intended to be used via redirection.
My professor gave us a txt file to use to test if our program works. It reads in ~1000 numbers (so we wouldn't have to manually enter them). But I don't know the linux command on how to use this txt file.
ccarri7#ubuntu:~/C$ ls
ccarri7lab2 ccarri7lab2.c lab2input.txt
ccarri7#ubuntu:~/C$
This is the folder where my executable/source/txt file are.
./ccarri7lab2 < lab2input.txt
will use the text in lab2input.txt as arguments for ccarri7lab2
http://linux.about.com/od/itl_guide/a/gdeitl42t01.htm
Did you try
ccarri7lab2 < lab2input.txt
Hope this is what you want, else you can give some more info.
Related
steps:
Let's say I have a C program inputFileName.c
I run inputFileName with input redirection such as ./inputFileName < file
How can I print the name of the file in my C program that I have typed in the terminal as an input redirection file?
The input redirection is a function of the shell. Your inputFileName executable see this as standard input. Depending on the exact operating system, you may be able to use system-specific functions to get the information you want, but there is not a standard means of doing so.
Input redirection can be achieved not only with the '<' symbol, but also with '|'.
program < filename
is equivalent to
cat filename | program
From there, one could go to
cat file1 file2 file3 | program
You begin to see why the initial 'stdin' for an executable cannot and does not have a "filename" associated with it.
If input comes from a pipe, there can't be an associated filename. Also if the file has been deleted or moved before closing the file descriptor, there is no associated filename. A file can have multiple names. In that case there are multiple filenames.
Given that, the "associated filename" of a file descriptor doesn't really make much sense. And even if you could get that info, using the filename in any way might make race conditions an issue.
The linux kernel does try to track an associated filename if a file descriptor was created by opening a file. But the keyword here is "tries".
If you are running Linux, you can find the filenname for standard input as a symlink under "/proc/self/fd/0". Just remember that you should not rely on that name for anything more than debug or display purposes.
so basically I have a C program which does a lot of computation based on an input .txt file and outputs a value. I want to run it 100 times and then work out the average, obviously this would be tedious to do individually.
So I've tried to research a bit about scripting etc and I've found things like this:
https://answers.yahoo.com/question/?qid=20091206100348AAaJPP8
Am I supposed to just do this in my command prompt? (I'm on Windows btw)
Thanks for any help :)
You're on Windows, so you can use a DOS batch script (.bat) to run your program N times using a loop (or N separate commands if that's easier for you). Use the >> symbol at the end of the command to append the output to a file. See http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/redirection.mspx?mfr=true for more info on this, and search google for dos bat file for help on getting started with writing batch scripts.
Try this:
Have the program append the data into the text or csv file concerned and then write another program where you can run the program for a defined number of times. Use the function system(). It accepts a string as argument and executes it in the CUI.
Hope that helps.
I am using a C program which takes file contents as input. I am using input redirection at the command line to read the file. Can I use getchar() to obtain the content of the file? Or should I be reading it into a certain array and then access it?
Yes sure you can use any method to read input from file while running program through command.
You do not need to format it at all. the data in file should appear as if typed on command line while providing inputs. May be this helps.
Please provide more insight if this does not help.Thanks
This might sound like a retarded question but I am just learning C and all the websites I looked at this showed you the command to do it (project < somefile.txt) but not where to do it. Does it go in my project somewhere or command prompt? And if it is command prompt how do I get to where I need to enter it?
It goes on your command prompt. You first need to cd into location where your compiled binaries are. That command basically says "run project and feed contents of somefile.txt into it"
If you're on Windows hit Win+R and run cmd. On UNIX you should find terminal app somewhere in your menu.
Write your C code to use the built in FILE pointers defined in stdio.h. Read from STDIN and write to STDOUT. When you run your command like this: project < somefile.txt, the shell will open somefile.txt as STDIN before your program runs.
I am stuck/struggling with a problem I am trying in C(Linux) using API calls(only) to copy multiple input files via command line into one output file. I have searched the Internet for answers but none seem to solve.
My program allows me to specify multiple input files and one output file via the command line. For example:
./archiver file1.txt file2 file3 file4 outputfile
I read these parameters using argc/argv. For some reason when I do ls -l, ./archiver and outputfile have the same number of bytes, thus meaning none of my input files have been copied to my outputfile, just whatever was in memory (when I do cat outputfile it shows a bunch of these )
None of the contents from my input files are in my output files.
Please could you help me as after those bunch of "" I don't know what to do I have tried reading up on malloc() etc. but I don't know how to implement that or if thats even relevant here.
Any help is appreciated, thanks for your time.
file_desc_in = open(argv[i],O_RDONLY,0);
//NEED a loop to copy multiple files in...
while (!eof) {
bytes_read = read(file_desc_in, &buffer, sizeof(buffersize));
if (bytes_read > 1)
bytes_written = write(file_desc_out, &i, bytes_read);
else {
eof=1;
}
I haven't included the errors but I do have them. Thanks for replying immediately.
It'd help to see your code. There's not a lot here to go on, but I'm going to take a wild guess. I suspect you're copying the file specified by argv[0] (your program) and not getting the rest. I don't think I can do any better with what you've given.
You say you are only using API calls. What API are you talking about? The POSIX API? The standard C file I/O API?
If you are just combining input files, you don't really need to write a C program to do it. Since you are running Linux, try using the shell command cat input1 input2 input3 > output.
If you must write a C program to do it, start simple. Before you actually do any file I/O, make sure that you can interpret the input arguments correctly. Have your program simply read in the command-line input and print out something like this:
Input files: file1.txt file2.txt file2.txt
Output files: outputfile.txt
That way, you can verify that your CLI parsing code works correctly before you start worrying about file I/O. It's much easier to debug things one piece at a time.
Your outer loop needs to open each filename, and close it at the end of the loop. You close the output file at the very end, after all the input files are read.
You should also learn the difference between open, read, write and fopen, fread, fwrite.