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#1
April 10th, 2002, 10:54 PM
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opening a C file from a specific directory
a few questions:
1) i'm writing a program that requires the opening of a file from a specific directory. i know the syntax to create a pointer to a file, however i am unclear as to how i could set the pointer to open a file like this: /home/username/./somedir/filename -- also how do i write the file back to that directory once i've made my editions to it? 2) how do i call system commands from a C program. for example how would i make the app call xmms for example /usr/bin/xmms ? 3) what is the syntax for setting up your main() to receive parameters from the command line? feedback on any of the above is appreciated. thanks! -j
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#2
April 11th, 2002, 12:35 PM
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1. Specify the complete pathname in the fopen function
Code:
#include <stdio.h>
....
....
FILE *in, *out;
/* To open a file in read mode */
in = fopen("/home/username/./somedir/filename", "r");
/* To open a file in write mode */
out = fopen("/home/username/./somedir/filename2", "w");
/* To open a file in append mode */
out = fopen("/home/username/./somedir/filename2", "a");
/* To open a file in read/write mode */
in = fopen("/home/username/./somedir/filename", "r+");
2. Use the system() call Code:
#include <stdlib.h>
....
....
system("/usr/bin/xmms");
3. Declare the function as: int main(int argc, char *argv[]) or int main(int argc, char **argv) argc will give you the number of arguments that are passed to the program and the argv array holds the actual arguments. argc will always be >=1 and argv[0] always holds the name of the program itself. Code:
#include <stdio.h>
int main(int argc, char *argv[]) {
int x;
for (x = 0; x < argc; x++)
printf("Argument #%d is %s\n", x, argv[x]);
return 0;
}
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