I create a simple file, using flex, it generate a file lex.yy.c, for now, I want to put it to C++ program.
%{
#include < stdio.h>
%}
%%
stop printf("Stop command received\n");
start printf("Start command received\n");
%%
When I type start or stop in command line, there is a output. What I want to do is to give the input by my C++ program, and the output of it should be sent to a variable in my program, is it possible? Thanks a lot!
I know the code I post is quite simple, but the result I imagine is:
create c file by flex and bison, and I use it as a header, so in the c++ program, I just need to call a function lex_yacc() to use it. ex. lex_yacc() is a calculator, so I sent an expression with evariables to this function, and it will return the result. I want to use this function in a C++ program, I am confused...Thanks a lot!
See the section about multiple input buffers in the manual. Especially the section about yy_scan_string and yy_scan_bytes.
For the "output", of course the is "output" when you give "stop" or "start" as input, you explicitly do that (i.e. the printf calls). You can put any code you want there.
Related
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.
I have a program I am writing, I have already completed it, but the requirement/specification for it says that:
In the "Command Prompt", if someone runs your program like this:
Peter David < savednames.txt
it should print out the names inside savednames.txt that matches each of "Peter" and "David"
I have written the program but my own is interactive, i.e it asks for the file, then the name you want to search for, and then it prints the matches.
It works perfectly fine, but I don't understand what the running of the program in command prompt like this: "Peter David < savednames.txt" means. I am using C++ on Microsoft Windows.
Please I need your help to explain it and how to implement it in my code...is it some kind of operator overloading or ...I don't understand!
On the command line, < is used for input redirection. The shell opens the file whose name follows the < and copies its contents into standard input for the program.
So if you called program input.txt, you could open the file and read its contents using std::ifstream or whatever; if you called program < input.txt, you could just read the file's contents from stdin using cin.
You can also do the same for output. Instead of opening a file and writing to it in your code, write to stdout and call your program as program > output.txt.
yourprogramname Peter David < savednames.txt
means that your program will be called with Peter as first argument, David as second argument, and its standard input will be connected to a stream reading out of savednames.txt.
You just need to read standard input one row at a time, and process it according to the arguments you received.
You just need to modify the code you already have to take the names from the command line (is there a limit? Could there be three names? Or four? You need to consider that) and to read the data from standard input stream, without any need of opening a file.
What I'd like to do is have my C++ code open up Mplus (statistical program that I've downloaded on my computer) and run it. Is it possible?
You may be able to do what you want with std::system() calls like:
std::system("program -e input_commands.txt"); // Assuming it accepts some sort of command line args
std::system("program < input_commands.txt"); // Assuming it responds to stdin
It depends on the program if this approach will work.
I have a two C++ source code in which one code generates an array for the specified input while other has to use array for execution. I want to know how can I link two C++ file such that output of the first file is the input for second one ?
Since they're separate programs, that means they each have a main() function. Because of that you can't link them together. What you can do, however, is use the shell to redirect the output from one program to the input of another. For example:
program1 | program2
The above creates a so-called "pipe". What it does is feed program2 with the output of program1. Only the standard input and standard output are redirected that way. In C++ that means std::cin and std::cout. Anything printed on std::cerr or std::clog is not redirected, so make sure to never print errors, warnings or other status/informational messages on std::cout. Only print the payload data and use std::cerr or std::clog for anything else.
Linux: Compile both files and push the content of the first to the second binary with a pipe in terminal else use a socket.. you can try to ouput the data with a binary-stream and the second binary can use the same techniqe to pushs it into a array.. i hope that helps you..
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.