I need to control a program in c++ (windows), I need to call it, then pass data to it as I collect it, finally after a certain command that program will use that data.
I need to open the prog.exe and then line by line or value by value supply it information, it works manually through cmd.
I have tried system() but this will stop after I open the program.
I need something like this.
//call it
prog.exe
//add data
DataStart
Data 1 [2 34 454 5]//etc
DataEnd //the program will take it from here.
all being passed though command line
There are different ways you could do this - if your program needs to execute part of the way through your code before getting the data as input, you can just use standard input, and prompt the user to type the data. If you want to use variable values for the input, but you will know them before execution, you can pass the information as command line arguments, where you will execute like so
prog.exe 1 2 3
and your program will access the data via argv[i] where i corresponds to each command line argument.
have your program read from standard input, and from the command line 'pipe' the result of the other program to yours
eg.
datagenerator.exe | prog.exe
assuming that datagenerator.exe writes to standard output, the | character will redirect the output to prog.exe's standard input
Related
I want to take data from 'input.txt' to run 'main.exe' and then save the result of that program with this data to 'output.txt'.
If possible, I would like to write wwith form <input.txt> <output.txt>.
First you need to compile your c++ program, then run it with the two parameters. See cplusplus.com for some tutorials on file in and file out and the resource for taking in command line arguments: https://www.geeksforgeeks.org/command-line-arguments-in-c-cpp/
I have this set of .gz files and inside each of them is a single text file. This text file needs to be used in a C program. The following code solves this problem somehow where parameters 1 and 2 are integers which I'm receiving as arguments for the C program (argc, argv[]) in main().
gzip -dc xyz.txt.gz | ./program parameter1 parameter2
Can someone explain how the above code works in command line?
How does the text file automatically get passed to the program?
Do I need to write extra code in the C program to receive this text file?
The shell connects the stdout of one command directly to the stdin of the other command through a pipe(7). Neither program has to do anything out of the ordinary to take advantage of this.
How can I save all the input(cin) and output(cout, cerr) from a program whose input is taken from file(using "<")? I would like the input and output to be in order(so each input is followed by corresponding output as if I were typing the input in myself).
I tried ">" to output everything to a file, but that only saves standard output(no input/cerr), and just plainly copying the command line output still only gives the output without the input(because of how "<" works).
Is there a way to write everything(output+input) to file in order?
EDIT: edited for clarity
EDIT2: I just realized that it's impossible to do what I'm trying to do since the console does not know anything about when the commands would actually be entered. I'll have to manually enter commands and use the "script" command to actually log all input/output.
You need to add cerr to the stream
command > file 2&>1
This means put 2 (stderr) to 1 (stdout) as well.
Actually I have trouble naming the title of this post. Because I don't know how to summarize my meaning in a professional way. But I'll explain my question as below:
I'm running a program written by C++, command is:
./VariationHunter_SC
Then it'll let you type in many parameters:
Please enter the minimum paired-end insert size:
Please enter the maximum paired-end insert size:
Please enter the pre-processing mapping prune probability:
Please enter the name of the input file:
Please enter the minimum support for a cluster:
Obviously I need to type in such parameters one by one to run the program; But I have thousands of such jobs, and need to pre-assign such parameters in script, and submit script to computer.
So how can I do that?
thx
Edit
so how can I make parameter-list?
Just like below?:
140
160
0
mrfast.vh
1
Seems the program cannot recognize these numbers, and distribute numbers..
This depends on how the program actually reads the data that you type in - it's likely that its reading stdin, so you could use separate files with the parameters and pass them in via redirection: ./VariationHunter_SC < parameter-file
It's also possible that the program will accept parameters on the command line, but there's no way of really knowing that (or how) except by whatever documentation the program might come with (or by reading the source code, if it's available and there is no other accurate docs).
Simply use the piping character to pipe the contents of a file to your program
example, in a windows command shell:
echo "asdf" | pause
This will pass "asdf" to the pause program. As a result, pause will print a "Press any key to continue" message, then imediately continue because it will receive the "asdf" string as a response.
So, overall, write or use a program that outputs the contents of your file. Call it, then pipe its output to the program that needs the input.
The unix cat command is such a command that writes the contents of a file to output, or to the input of another executable if you are piping the output.
I am having trouble using system() from libc on Linux. My code is this:
system( "tar zxvOf some.tar.gz fileToExtract | sed 's/some text to remove//' > output" );
std::string line;
int count = 0;
std::ifstream inputFile( "output" );
while( std::getline( input, line != NULL ) )
++count;
I run this snippet repeatedly and occasionally I find that count == 0 at the end of the run - no lines have been read from the file. I look at the file system and the file has the contents I would expect (greater than zero lines).
My question is should system() return when the entire command passed in has completed or does the presence of the pipe '|' mean system() can return before the part of the command after the pipe is completed?
I have explicitly not used a '&' to background any part of the command to system().
To further clarify I do in practice run the code snippet multiples times in parallel but the output file is a unique filename named after the thread ID and a static integer incremented per call to system(). I'm confident that the file being output to and read is unique for each call to system().
According to the documentation
The system() function shall not return until the child process has terminated.
Perhaps capture the output of "output" when it fails and see what it is? In addition, checking the return value of system would be a good idea. One scenario is that the shell command you are running is failing and you aren't checking the return value.
system(...) calls the standard shell to execute the command, and the shell itself should return only after the shell has regained control over the terminal. So if there's one of the programs backgrounded, system will return early.
Backgrounding happens through suffixing a command with & so check if the string you pass to system(...) contains any & and if so make sure they're properly quoted from shell processing.
System will only return after completion of its command and the file output should be readable in full after that. But ...
... multiple instances of your code snippet run in parallel would interfere because all use the same file output. If you just want to examine the contents of output and do not need the file itself, I would use popen instead of system. popen allows you to read the output of the pipe via a FILE*.
In case of a full file system, you could also see an empty output while the popen version would have no trouble with this condition.
To notice errors like a full file system, always check the return code of your calls (system, popen, ...). If there is an error the manpage will tell you to check errno. The number errno can be converted to a human readable text by strerror and output by perror.