12. Directory walk

Make directory 12_Permissions and cd there.

0. On filename patterns:

   • Special characters: «*», «?», «[characters]»:

        1 $ ls /usr/bin/no*
        2 /usr/bin/nohup    /usr/bin/nosetests3   /usr/bin/nosetests-3.7
        3 /usr/bin/nomarch  /usr/bin/nosetests-3
        4 $ ls /usr/bin/n?c*
        5 /usr/bin/nick2ldif  /usr/bin/nmcli
        6 $ ls /usr/bin/n[a-e]*
        7 /usr/bin/namei    /usr/bin/ncdu                /usr/bin/neqn           /usr/bin/newgrp
        8 /usr/bin/nano     /usr/bin/ncurses5-config     /usr/bin/net
        9 /usr/bin/natspec  /usr/bin/ndg_httpclient.py3  /usr/bin/netcat
       10 /usr/bin/nc       /usr/bin/neotoppm            /usr/bin/netpbm-config
       11 $ ls /usr/bin/n[a-ex]*
       12 /usr/bin/namei    /usr/bin/ncdu                /usr/bin/neqn           /usr/bin/newgrp
       13 /usr/bin/nano     /usr/bin/ncurses5-config     /usr/bin/net            /usr/bin/nxproxy
       14 /usr/bin/natspec  /usr/bin/ndg_httpclient.py3  /usr/bin/netcat
       15 /usr/bin/nc       /usr/bin/neotoppm            /usr/bin/netpbm-config
       16 
     

   • see glob for more

1. Write a program that uses unlink to remove files:

   • ./deletefile file1 file2 …

2. Write a program than uses opendir, readdir and closedir to list a directory content

   • ./lsdir /usr/share/dict

   • ./lsdir .

   • modify this program to show file object type (using dirent->d_type as documented in readdir)

3. Copy this program to a new one, lsdir2.c an modify it:

   • define a function listdir(char *path) that performs all the listing and refactor the code:

        1   …
        2   int main(int argc, char *argv[]) {
        3         listdir(argv[1]);
        4         return 0;
        5 }
     

   • filter out «"."» and «".."» directory entries

     • e. g (suppose we are in while(…readdir()…) cycle):

          1                 if(!strcmp(dirent->d_name, ".") || !strcmp(dirent->d_name, ".."))
          2                         continue;
       

   • check every next file object to be a directory (see readdir) and mention this

     • e. g.

          1                 if(dirent->d_type == DT_DIR)
          2                         printf("%s: directory\n", dirent->d_name);
          3                 else
          4                         printf("%s: %d\n", dirent->d_name, dirent->d_type);
       

4. Copy this program to a new one, lsdir3.c an modify it:

   • to accept two parameters: a directory and a pattern

   • display only entries that apply the pattern via fnmatch

   • e. g. ./lsdir3 dir "fil*.1?" for matching fil.11, files.01.1a but not file11 nor files.01.1bc

     • Note «"…"» around the pattern

H/W

• Finish all 4 tasks