This question already has an answer here:
how to run a batch file using c++?
(1 answer)
Closed 8 years ago.
I want to run an .exe file from my c++ program.
but I also want to pipe an input file and take output of that file into another file.
I know that this can be done from command line as:
c:> my_program.exe <"input.txt"> "output.txt"
with this command, my_program takes all standard input from input.txt and gives standard output to output.txt
Now I want this should happen from my C++ program.
my my_program.exe is in D: drive. also input.txt is in D: drive.
Please tell me how can I accomplish my goal.
You need to handle input and output pipes inside your c++ program, and read/write data to files accordingly. See MSDN for example.
The question was basically how to redirect stdin and stdout from the inside of C++, which as been answered here.
Just change your directory to D:
cd D:\
D:>my_program.exe <"input.txt">"output.txt"
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.
This question already has answers here:
In C how do I print filename of file that is redirected as input in shell
(9 answers)
Closed 7 years ago.
I'm trying to make my program output everything I typed into the command line but the file I streamed to it is not printing out because it doesn't get stored in argv. Here is how I execute:
Input:
./program < file.txt
Expected output:
./program < file.txt
Actual output:
./program
Just to be clear I don't want to print out what is in the file. I only want to print out the name of the file.
File redirection is handled by the shell, not by the program. When the shell sees "<" it basically says "when you start this program, map stdin to this file instead of the terminal". So, under the hood, the shell does fork(); followed by closing and opening the file in it's place, then calls execv() or similar to actually execute the program. Similarly, if you do ./program *.txt, by the time the program sees the command line, *.txt has been expanded to all of the matching filenames in the directory.
I doubt, it's a stream of data, filename is not being streamed to the program
Besides, I don't think you should look for the input in argv, you should read stream contents from stdin, e.g. using scanf's
This question already has answers here:
system("c:\\sample\\startAll.bat") cannot run because of working directory?
(4 answers)
Closed 9 years ago.
Consider the following:
I have a c++ program in C:\Documents\myProgram.exe
With this code in it:
system("start C:\\somefolder\\start.bat");
That will start the target file (start.bat) in C:\Documents\ instead of `C:\somefolder\'.
My question is, how do I execute the file in it's own directory instead of myProgram's directory?
In theory this is what I want to accomplish using c++:
cd C:\somefolder\,
start start.bat
If you're on windows anyway, use ShellExecute, you can set more things and launch even documents, links etc.
To do this you can do one of two things (that I found).
A) You can use chdir() in unistd.h; see http://pubs.opengroup.org/onlinepubs/7908799/xsh/unistd.h.html
or
B) You can use something called the File System Interface, from the GNU library, for more advanced stuff; see http://www.gnu.org/software/libc/manual/html_node/File-System-Interface.html#File-System-Interface.
Anyway, best of luck, I hope you find something that will work!
This question already has answers here:
How do I execute a command and get the output of the command within C++ using POSIX?
(12 answers)
How to assign shell command output to a variable in C language
(4 answers)
Closed 9 years ago.
I want to execute a script through a c++ program and get its output. Presently I am doing
system("./script.sh > out.txt");
But I need a command that get the output to a string, some thing like:
out = system("./script.sh");
printf(out);
I can't read the file out.txt after execute the script because I don't have permission to that. I deployed my c++ program at other framework (boinc) that doesn't give me this permission.
Does anybody have a hint?
Thanks in advance!
Felipe
you can use popen() and then get the output of the command from the pipe opened by popen()
FILE *fp;
fp=popen("./script.sh","r");
and to get your output. you can use fgets() or fread() to read from pipe like you read from a file
This question already has an answer here:
Closed 11 years ago.
Possible Duplicate:
How to get drive label in Linux using C from userspace
How can I obtain label of a disk by its file name (/dev/sda1, e.g.) in a program written in C/C++?
You can code the C or C++ equivalent of this command:
find -L /dev/disk/by-label -inum $(stat -c %i /dev/sda1) -print
That is, stat() the device file you care about and remember its inode number. Iterate over all of the files in /dev/disk/by-label, and stat() each of them. When the inode number matches, then the name of the matched file is the label of that disk.
If it were me, I'd code the above algorithm in C++, using Boost.Filesystem.