I am accepting the path through command line input.
When I do
dir=opendir(args[1]);
it doesn' t enter the loop...i.e dir==null
...
How do I pass the command line input to dir pointer?
void main(int c,char **args)
{
DIR *dir;
struct dirent *dent;
char buffer[50];
strcpy(buffer, args[1]);
dir = opendir(buffer); //this part
if(dir!=NULL)
{
while((dent=readdir(dir))!=NULL)
printf(dent->d_name);
}
close(dir);
}
./a.out /root/TEST is used to run the program..
./a.out --> to execute the program
/root/TEST --> input by the user i.e valid path
Parameters passed to the C program executable is nothing but an array of string(or character pointer),so memory would have been already allocated for these input parameter before your program access these parameters,so no need to allocate buffer,and that way you can avoid error handling code in your program as well(Reduce chances of segfault :)).
Here is a simple way to implement ls
command using c
. To run use for example ./xls /tmp
#include<stdio.h>
#include <dirent.h>
void main(int argc,char *argv[])
{
DIR *dir;
struct dirent *dent;
dir = opendir(argv[1]);
if(dir!=NULL)
{
while((dent=readdir(dir))!=NULL)
{
if((strcmp(dent->d_name,".")==0 || strcmp(dent->d_name,"..")==0 || (*dent->d_name) == '.' ))
{
}
else
{
printf(dent->d_name);
printf("\n");
}
}
}
close(dir);
}
Some feedback on the segment of code, though for the most part, it should work...
void main(int c,char **args)
int main
- the standard defines main
as returning an int
.c
and args
are typically named argc
and argv
, respectfully, but you are allowed to name them anything...
{
DIR *dir;
struct dirent *dent;
char buffer[50];
strcpy(buffer,args[1]);
args[1]
is longer than 50 bytes, buffer
will not be able to hold it, and you will write to memory that you shouldn't. There's no reason I can see to copy the buffer here, so you can sidestep these issues by just not using strcpy
......
dir=opendir(buffer); //this part
If this returning NULL
, it can be for a few reasons:
./your_program my directory
, which will fail, because it tries to opendir("my")
)Source: Stackoverflow.com