Open directory using C

Question

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- gt d name             close dir        a out   root TEST is used to run the program     a out -- gt  to execute the program  root TEST -- gt  input by the user i e valid path

User · Answer

Here is a simple way to implement ls command using c  To run use for example   xls  tmp       include lt stdio h gt       include  lt dirent h gt      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- gt d name       0    strcmp dent- gt d name        0      dent- gt d name                                               else                         printf dent- gt d name           printf   n                                                          close dir

User · Answer

You should really post your code a   but here goes  Start with something like        include  lt stdio h gt       include  lt dirent h gt       int main  int argc  char  argv              struct dirent  pDirent          DIR  pDir              Ensure correct argument count           if  argc    2                printf   Usage  testprog  lt dirname gt  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- gt 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

User · Answer

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

User · Answer

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       You have a buffer overflow here  If 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    The directory didn t exist   Did you type it right  Did it have a space in it  and you typed   your program my directory  which will fail  because it tries to opendir  my    You lack permissions to the directory There s insufficient memory   This is unlikely

[c] Open directory using C

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