I am accepting the path through command line input.
When I do
dir=opendir(args[1]);
it doesn' t enter the loop...ie 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
You should really post your code (a) , but here goes. Start with something like:
#include <stdio.h>
#include <dirent.h>
int main (int argc, char *argv[]) {
struct dirent *pDirent;
DIR *pDir;
// Ensure correct argument count.
if (argc != 2) {
printf ("Usage: testprog <dirname>\n");
return 1;
}
// Ensure we can open directory.
pDir = opendir (argv[1]);
if (pDir == NULL) {
printf ("Cannot open directory '%s'\n", argv[1]);
return 1;
}
// Process each entry.
while ((pDirent = readdir(pDir)) != NULL) {
printf ("[%s]\n", pDirent->d_name);
}
// Close directory and exit.
closedir (pDir);
return 0;
}
You need to check in your case that args[1]
is both set and refers to an actual directory. A sample run, with tmp
is a subdirectory off my current directory but you can use any valid directory, gives me: testprog tmp
[.]
[..]
[file1.txt]
[file1_file1.txt]
[file2.avi]
[file2_file2.avi]
[file3.b.txt]
[file3_file3.b.txt]
Note also that you have to pass a directory in, not a file. When I execute:
testprog tmp/file1.txt
I get:
Cannot open directory 'tmp/file1.txt'
That's because it's a file rather than a directory (though, if you're sneaky, you can attempt to use diropen(dirname(argv[1]))
if the initial diropen
fails).
(a) This has now been rectified but, since this answer has been accepted, I'm going to assume it was the issue of whatever you were passing in.
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")
) 传递给 C 程序可执行文件的参数只不过是一个字符串数组(或字符指针),因此在您的程序访问这些参数之前,已经为这些输入参数分配了内存,因此无需分配缓冲区,这样您就可以避免程序中的错误处理代码(减少段错误的机会:))。
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);
}
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