So, I am working on an application that reads files, much the way vim or cat would, where you type "appname /path/to/file.txt" and it passes the file path as a perameter to the program which manipulates the file in some way.
I have run into a roadblock though. In vim, cat, or a similar program, you can type "appname file.txt", and it will read the file in the current directory that you launch the application from terminal in.
For example, I want to edit a file my documents directory. I type "cd ~/Documents", and then I can either type "vim ~/Documents/Essay.txt", or I just can type "vim Essay.txt".
My application will be stored in a binary file in the /bin/ directory so I can launch it from anywhere using the Terminal, but how do I pass the path name of the directory I am in when I call it from terminal?
As I am a new Linux developer (I have always worked with the .NET launguages in Windows) I am not sure weather this is handled by the Linux terminal, or by the C application itself.
Any help or suggestions would be much appreciated!
Also, if there is a more efficiant way to run it from the terminal than sticking it in the /bin/, let me know.
If you want to get the directory the process was run from you can use the system call getcwd to copy a string into a buffer and return it. The kernel keeps track of this for every process.
e.g.
char buf[100];
printf("Current directory: %s\n", getcwd(buf, 100));
The working directory can be changed, but will default to where the process launched.
This should work just fine without you having to do anything special. Did you try something that didn't work as you expected?
Generally you don't put user programs in /bin. I would store your program in /usr/local/bin.
https://unix.stackexchange.com/a/8658
Related
i have a trouble with :
system("cd mypath");
when i try this in C programming language terminal doesn't do anything.
i need help.
The system function creates a whole new process, separate from the one calling the function.
Each process have its own current working directory associated with it, and this working directory is specific to that process only. Changing the working directory of one process will not change it for another process.
If you want to change the working directory of your own process use operating-system specific functions to to it. Like chdir on Linux (and other POSIX system like macOS), or SetCurrentDirectory in Windows.
Note that if you change directory in your own process, the directory of the shell or console that invoked your program will not be changed, as it's also a separate process from yours.
look just do
chdir("path");
or
system("chdir PATH"); //linux
I need to make a game in C for my finals. The user should input the map file he wants to play.
Here's my simple code:
int main(){
FILE *map;
char fileToRead[100];
do{
printf("Insert file name: ");
fgets(fileToRead, 100, stdin);
map = fopen("/Users/rajunior/Desktop/map_2.txt", "r");
//map = fopen(fileToRead, "r");
printf("%s", fileToRead);
If I use the "map = fopen("/Users/rajunior...)" hardcoded, it works!
But I need to use the second (commented) option; the first one is useless for my purpose.
In other words, I need the fileToRead to be in the same directory as my .c, but how?
screenshot: https://imgur.com/a/DbX9tw4
Option 1: Install the command line tools. Put the C file and the text file in the same directory. Open a terminal window. Compile and run from the command line. If I recall correctly, the command line tools download can be found in Preferences.../Downloads.
Option 2: Go to the Product/Scheme/Edit Scheme... menu. When the dialog box appears, select Run at the left and Options at the top. Then look for Working Directory. Set the working directory to point to the directory where the text file is.
This was going to be a comment, but it is too long for comfort.
You'll need to know the current directory of the process when it is run. If you run it from the shell, the current directory of your program will be the same as the current directory of the program. If you run it from within XCode, I've no idea what the directory will be, but it probably won't be where the source is — it'll be in a build directory of some sort, probably.
Your program can find out where it is run from with getcwd(). Then you'll be able to tell how to chdir() to the directory where the source is (as long as the program knows where the source is, because you told it somehow — argument or command line variable, or …). Or you can determine how to create a relative path name that will find the file in the source directory.
There's probably an XCode (maybe Objective-C) way to find the information, perhaps via plists.
I don't code for a Mac; I only code on a Mac, and I run XCode itself rather seldom.
I'm calling a C executable compiled using Cygwin in MATLAB, using the unix() function. This works fine, and I can see the desired output on the MATLAB command window. However, there is an fprintf() inside the executable that is supposed to create and write to a text file which does not run - no such file is created. The text file is created just fine when I run the executable directly through Cygwin.
I was wondering if I need to grant permissions to the MATLAB file/executable to enable this? How could I go about this?
What path are you using to create the file? It might have been created -- just not where you expected it.
If it's a relative path, you could use getcwd(2) inside your C program to get and print the working directory (or e.g. getpid(2) to get the PID and then do ls -d /proc/<pid>/cwd, which will work on Linux at least). Once you have the working directory, check if the file is somewhere in there.
If it looks like the file really isn't being created, my next step would be to add some error checking to functions and print messages for errors to try to figure out what's going on. strerror(3) and perror(3) might come in handy.
I'm programming in C, and
I have the following problem:
I use fopen and try to read from a csv file, that is currently storred in the folder of the exe file of the program.
the program works fine in debug mode and release mode, but when I try to run the program in "start without debugging" on visual studio 2008 express edition, the program stops working and windows is showing a message: "*.exe has stopped working. a program caused the program to stop working correctly. windows will close the program and notify you if a solution is available".
I've tried running the program on several computers, and it's the same.
another information I can give you is that if I enter the full path of the file (C:....file.csv) - then is works just fine, without any problem.
I know I didn't write any code, but I hope someone will have an idea why this can happend.
thanks is advance.
Your program is not finding the csv file, fopen() fails and return a null pointer, you try to use it without checking and your program crashes (just my guess).
Firstly, you must make a check to see if fopen() could indeed open your file:
FILE* f = fopen("file.csv", "r");
if(f == NULL) {
/* print some meaningful error */
} else {
/* use the file */
}
Secondly, you may solve the problem by executing your program from the same folder the file is present. I am not a Windows guy, but if you create a link to the ".exe", in its properties may have some configuration called "Working Directory" or something like that, that you may set to the path on where the file can be found.
Every process has a working directory, that is usually the directory from where it was started, though it may be inherited from the parent process and it may be changed programmatically. If you do not specify the full path when loading a file, the process will search for the file in its current working directory.
I am using Ubuntu Lucid Lynx
is it possible to write data in a file through a C program which has read only permission. If it's not possible, then is there any way to give sudo access to the C program.
For files without permissions, I would save the data in a string. Then i would open the file with write option:
FILE *fp = fopen(file_path,"w")
fputs(string,fp);
fclose(fp);
No you cannot write to a read-only file, that would undermine the whole point of read-only. As for giving root access to a c program, you could always run it as root or as someone who has permissions to modify the file.
If you are the owner of the file you can change the permissions with chmod. If you are not the owner you can use setuid bit to acces the file, but this really should be avoided.
It is not possible to have the program elevate itself to sudo status while its running.
And that is a bloody good thing.
If that was possible every virus would have the ability to take over any system.
The program needs to be started with the proper access-rights from the start.
In Unix generally what you'd want to do is make the program's executable owned by root, world executable, then set the SUID bit on it.
chown root filename
chmod 4775 filename
See chomd docs for exactly what the bits mean, but all together this means that whenever someone runs this executable, they get the executable process' user ID set to the owner's (root).
You can, but not in a standard cross-platform way.
On Unix systems, use chmod. It should be in <sys/stat.h>
See this link.
If you need root privilage, try:
if(fp == NULL)
execvp("sudo", argv);