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Still new to perl
Joined: 07 May 2004
Posts: 7
Still new to perl
I tried the sort function and it`s not working because I know my code
is wrong. Could someone shed some light as to what I`m missing here?
Below is the actual piece of code that attempts to use the sort
function.
open (IN,"ssh $srv_name cat /etc/passwd|") || die "Cannot open file
on $srv_name";
while (<IN>)
{
@uid_sort = $uid = (split /:/) [2];
if (($uid >= 20000) && ($uid <= 30000))
{
@users = sort { $a <=> $b } @uid_sort;
prt_uids();
}
}
The prt_uids is just a subroutine that prints out the uid`s nothing
big. Any help would be appreciated.
Joined: 05 May 2004
Posts: 16
Still new to perl
There are several logic issues, but let me go through the ones I found.
1) I don`t know what you want to do with the "ssh $srv_name cat
/etc/passwd|" line. If you want to open /etc/passwd for parsing just do
it directly:
open (IN,"</etc/passwd") || die "Cannot open passwd file";
2) Don`t do double assignments on commands you don`t even understand.
First split the input line, then assign element [2] to $uid. It is
clearer and it does the job. Also, it does not hurt to chomp the line
first:
while (<IN>) {
chomp; # Removes last newline
@uid_sort = split /:/; # splits line on ":"
$uid = $uid_sort[2]; # gets uid
3) At this point, you have an array @uid_sort with all the elements
from the line you are working on. If what the variable name and future
sort operation tell me, it seems you really want all $uid`s that lie in
the 20000-30000 range to be sorted and printed out. If this is what you
want, this is not what your program is givin you.
After step 1 and 2, you need to see if the $uid is in the range and if
it is, append it to your final array of uids. After the end of the loop
(which works on every line of /etc/passwd), you should then sort your
final uids array and print it out. This you do with
@users = sort { $a <=> $b } @uid_sort;
prt_uids(@users);
but as I tell you, these should be located outside of the main loop,
after processing all /etc/passwd lines.
Think about what you want your program to do before starting to code.
Review your steps and try again. I`m not giving you the complete
answer, but enough info to get it on your own.
Notice however that you need to use a second array to @uid_sort to
split the first line (@elements or whatever name you want, and then
$uid = $elements[2]).
Good luck.
Rex
--- perl_1978 <no_reply@yahoogroups.com> wrote:
> I tried the sort function and it`s not working because I know my code
>
> is wrong. Could someone shed some light as to what I`m missing here?
> Below is the actual piece of code that attempts to use the sort
> function.
>
> open (IN,"ssh $srv_name cat /etc/passwd|") || die "Cannot open file
> on $srv_name";
> while (<IN>)
>
> {
> @uid_sort = $uid = (split /:/) [2];
> if (($uid >= 20000) && ($uid <= 30000))
> {
> @users = sort { $a <=> $b } @uid_sort;
> prt_uids();
> }
> }
>
> The prt_uids is just a subroutine that prints out the uid`s nothing
> big. Any help would be appreciated.
>
>
>
>
> ------------------------ Yahoo! Groups Sponsor
>
>
> Yahoo! Groups Links
>
>
>
>
>
Joined: 07 May 2004
Posts: 7
Still new to perl
Actually, step 1 is fine because I`m going to a remote server and not
local.
As for step 2 and 3 - thanks for the advice about my crazy code. I
just needed a little push in the right direction. I will try your
advice.
--- In perl_official@yahoogroups.com, El Rex <rex@b...> wrote:
>
> There are several logic issues, but let me go through the ones I
found.
>
> 1) I don`t know what you want to do with the "ssh $srv_name cat
> /etc/passwd|" line. If you want to open /etc/passwd for parsing
just do
> it directly:
>
> open (IN,"</etc/passwd") || die "Cannot open passwd file";
>
> 2) Don`t do double assignments on commands you don`t even
understand.
> First split the input line, then assign element [2] to $uid. It is
> clearer and it does the job. Also, it does not hurt to chomp the
line
> first:
>
> while (<IN>) {
> chomp; # Removes last newline
> @uid_sort = split /:/; # splits line on ":"
> $uid = $uid_sort[2]; # gets uid
>
> 3) At this point, you have an array @uid_sort with all the elements
> from the line you are working on. If what the variable name and
future
> sort operation tell me, it seems you really want all $uid`s that
lie in
> the 20000-30000 range to be sorted and printed out. If this is what
you
> want, this is not what your program is givin you.
>
> After step 1 and 2, you need to see if the $uid is in the range and
if
> it is, append it to your final array of uids. After the end of the
loop
> (which works on every line of /etc/passwd), you should then sort
your
> final uids array and print it out. This you do with
>
> @users = sort { $a <=> $b } @uid_sort;
> prt_uids(@users);
>
> but as I tell you, these should be located outside of the main loop,
> after processing all /etc/passwd lines.
>
> Think about what you want your program to do before starting to
code.
> Review your steps and try again. I`m not giving you the complete
> answer, but enough info to get it on your own.
>
> Notice however that you need to use a second array to @uid_sort to
> split the first line (@elements or whatever name you want, and then
> $uid = $elements[2]).
>
> Good luck.
> Rex
>
> --- perl_1978 <no_reply@yahoogroups.com> wrote:
> > I tried the sort function and it`s not working because I know my
code
> >
> > is wrong. Could someone shed some light as to what I`m missing
here?
> > Below is the actual piece of code that attempts to use the sort
> > function.
> >
> > open (IN,"ssh $srv_name cat /etc/passwd|") || die "Cannot open
file
> > on $srv_name";
> > while (<IN>)
> >
> > {
> > @uid_sort = $uid = (split /:/) [2];
> > if (($uid >= 20000) && ($uid <= 30000))
> > {
> > @users = sort { $a <=> $b } @uid_sort;
> > prt_uids();
> > }
> > }
> >
> > The prt_uids is just a subroutine that prints out the uid`s
nothing
> > big. Any help would be appreciated.
> >
> >
> >
> >
> > ------------------------ Yahoo! Groups Sponsor
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
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