I have a perl script that works fine when I run it using perl filename, however when I use the command
perl -w logint > logintime.html
I get this error
Use of uninitialized value $days in multiplication (*) at logint line 5, <LAST> line 3.
It repeats this from line 3-47
This is the perl code
#!/usr/bin/perl
open LAST, "last |";
while (<LAST>) {
if (($name,$days,$hours,$mins) = /^(\w+).+\((?:(\d+)\+)?(\d+):(\d+)/) {
$TIMES{$name} += 1440 * $days + 60 * $hours + $mins;
}
}
foreach (sort keys %TIMES) {
print "$_ $TIMES{$_}\n";
}
This is how I'm attempting to output it.
#!/bin/bash
echo $HDR > ~/public_html/logintime.html
perl -w logint > logintime.html
echo $FTR >> ~/public_html/logintime.html
This is just a warning, it's not an error. You're seeing it when you run that command because '-w' is the warnings pragma.
You could also put it at the end of your shebang
#!/usr/bin/perl -w
Or 'use warnings;'. Anyway, the warning is just saying it doesn't have a value. It looks like you're reading the last log to see who last logged in, the output can be different depending on what OS you're on. I would confirm it's working as expected and getting the correct values.
It's also best practice to use 'use strict;'.
Related
For personal development and projects I work on, we use four spaces instead of tabs.
However, I need to use a heredoc, and I can't do so without breaking the indention flow.
The only working way to do this I can think of would be this:
usage() {
cat << ' EOF' | sed -e 's/^ //';
Hello, this is a cool program.
This should get unindented.
This code should stay indented:
something() {
echo It works, yo!;
}
That's all.
EOF
}
Is there a better way to do this?
Let me know if this belongs on the Unix/Linux Stack Exchange instead.
(If you are using bash 4, scroll to the end for what I think is the best combination of pure shell and readability.)
For heredocs, using tabs is not a matter of preference or style; it's how the language is defined.
usage () {
⟶# Lines between EOF are each indented with the same number of tabs
⟶# Spaces can follow the tabs for in-document indentation
⟶cat <<-EOF
⟶⟶Hello, this is a cool program.
⟶⟶This should get unindented.
⟶⟶This code should stay indented:
⟶⟶ something() {
⟶⟶ echo It works, yo!;
⟶⟶ }
⟶⟶That's all.
⟶EOF
}
Another option is to avoid a here document altogether, at the cost of having to use more quotes and line continuations:
usage () {
printf '%s\n' \
"Hello, this is a cool program." \
"This should get unindented." \
"This code should stay indented:" \
" something() {" \
" echo It works, yo!" \
" }" \
"That's all."
}
If you are willing to forego POSIX compatibility, you can use an array to avoid the explicit line continuations:
usage () {
message=(
"Hello, this is a cool program."
"This should get unindented."
"This code should stay indented:"
" something() {"
" echo It works, yo!"
" }"
"That's all."
)
printf '%s\n' "${message[#]}"
}
The following uses a here document again, but this time with bash 4's readarray command to populate an array. Parameter expansion takes care of removing a fixed number of spaces from the beginning of each lie.
usage () {
# No tabs necessary!
readarray message <<' EOF'
Hello, this is a cool program.
This should get unindented.
This code should stay indented:
something() {
echo It works, yo!;
}
That's all.
EOF
# Each line is indented an extra 8 spaces, so strip them
printf '%s' "${message[#]# }"
}
One last variation: you can use an extended pattern to simplify the parameter expansion. Instead of having to count how many spaces are used for indentation, simply end the indentation with a chosen non-space character, then match the fixed prefix. I use : . (The space following
the colon is for readability; it can be dropped with a minor change to the prefix pattern.)
(Also, as an aside, one drawback to your very nice trick of using a here-doc delimiter that starts with whitespace is that it prevents you from performing expansions inside the here-doc. If you wanted to do so, you'd have to either leave the delimiter unindented, or make one minor exception to your no-tab rule and use <<-EOF and a tab-indented closing delimiter.)
usage () {
# No tabs necessary!
closing="That's all"
readarray message <<EOF
: Hello, this is a cool program.
: This should get unindented.
: This code should stay indented:
: something() {
: echo It works, yo!;
: }
: $closing
EOF
shopt -s extglob
printf '%s' "${message[#]#+( ): }"
shopt -u extglob
}
geta() {
local _ref=$1
local -a _lines
local _i
local _leading_whitespace
local _len
IFS=$'\n' read -rd '' -a _lines ||:
_leading_whitespace=${_lines[0]%%[^[:space:]]*}
_len=${#_leading_whitespace}
for _i in "${!_lines[#]}"; do
printf -v "$_ref"[$_i] '%s' "${_lines[$_i]:$_len}"
done
}
gets() {
local _ref=$1
local -a _result
local IFS
geta _result
IFS=$'\n'
printf -v "$_ref" '%s' "${_result[*]}"
}
This is a slightly different approach which requires Bash 4.1 due to printf's assigning to array elements. (for prior versions, substitute the geta function below). It deals with arbitrary leading whitespace, not just a predetermined amount.
The first function, geta, reads from stdin, strips leading whitespace and returns the result in the array whose name was passed in.
The second, gets, does the same thing as geta but returns a single string with newlines intact (except the last).
If you pass in the name of an existing variable to geta, make sure it is already empty.
Invoke geta like so:
$ geta hello <<'EOS'
> hello
> there
>EOS
$ declare -p hello
declare -a hello='([0]="hello" [1]="there")'
gets:
$ unset -v hello
$ gets hello <<'EOS'
> hello
> there
> EOS
$ declare -p hello
declare -- hello="hello
there"
This approach should work for any combination of leading whitespace characters, so long as they are the same characters for all subsequent lines. The function strips the same number of characters from the front of each line, based on the number of leading whitespace characters in the first line.
The reason all the variables start with underscore is to minimize the chance of a name collision with the passed array name. You might want to rewrite this to prefix them with something even less likely to collide.
To use in OP's function:
gets usage_message <<'EOS'
Hello, this is a cool program.
This should get unindented.
This code should stay indented:
something() {
echo It works, yo!;
}
That's all.
EOS
usage() {
printf '%s\n' "$usage_message"
}
As mentioned, for Bash older than 4.1:
geta() {
local _ref=$1
local -a _lines
local _i
local _leading_whitespace
local _len
IFS=$'\n' read -rd '' -a _lines ||:
_leading_whitespace=${_lines[0]%%[^[:space:]]*}
_len=${#_leading_whitespace}
for _i in "${!_lines[#]}"; do
eval "$(printf '%s+=( "%s" )' "$_ref" "${_lines[$_i]:$_len}")"
done
}
I have a bunch of directories to process, so I start a for loop like this:
foreach n (1 2 3 4 5 6 7 8)
Then I have a bunch of commands where I am copying over a few files from different places
cp file1 dir$n
cp file2 dir$n
but I have a couple commands where the $n is in the middle of the command like this:
cp -r dir$nstep1 dir$n
When I run this command, the shell complains that it cannot find the variable $nstep1. What i want to do is evaluate the $n first and then concatenate the text around it. I tried using `` and (), but neither of those work. How to do this in csh?
In this respect behavior is similar to POSIX shells:
cp -r "dir${n}step1" "dir${n}"
The quotes prevent string-splitting and glob expansion. To observe what this means, compare the following:
# prints "hello * cruel * world" on one line
set n=" * cruel * "
printf '%s\n' "hello${n}world"
...to this:
# prints "hello" on one line
# ...then a list of files in the current directory each on their own lines
# ...then "cruel" on another line
# ...then a list of files again
# ... and then "world"
set n=" * cruel * "
printf '%s\n' hello${n}world
In real-world cases, correct quoting can thus be the difference between deleting the oddly-named file you're trying to operate on, and deleting everything else in the directory as well.
I am trying to write a Perl script to do an SNMP get. It should work like the following command:
snmpget -v 3 -l authNoPriv -a MD5 -u V3User -A V3Password 10.0.1.203 sysUpTime.0
Returns:
SNMPv2-MIB::sysUpTime.0 = Timeticks: (492505406) 57 days, 0:04:14.06
But my Perl script returns the following:
ERROR: Received usmStatsUnknownUserNames.0 Report-PDU with value 1 during synchronization.
Last but not least, here is the Perl script:
use strict;
use warnings;
use Net::SNMP;
my $desc = 'sysUpTime.0';
my ($session, $error) = Net::SNMP->session(
-hostname => '10.0.1.202',
-version => 'snmpv3',
-username => 'V3User',
-authprotocol => 'md5',
-authpassword => 'V3Password'
);
if (!defined($session)) {
printf("ERROR: %s.\n", $error);
exit 1;
}
my $response = $session->get_request($desc);
my %pdesc = %{$response};
my $err = $session->error;
if ($err){
return 1;
}
print %pdesc;
exit 0;
I called the Perl script and snmpget on the same (Linux) machine. What could be causing this and how can I fix it?
As PrgmError points out, you're using a different IP address in your Perl script than in your snmpget command; I would double check that. The particular error you're getting indicates that your username is wrong; if the IP mismatch was simply a typo in your question, I would double check the username next.
A few other points about your Perl script:
Use die
You should use die instead of printf and exit since die will print the line number where it was invoked. This will make debugging your script much easier if there are multiple places it could fail:
die "Error: $error" if not defined $session;
will print something like
Error: foo bar at foo.pl line 17.
Also, using return inside an if statement doesn't make any sense; I think you meant to use
if ($err) {
exit 1;
}
but you should die with the specific error message you get instead of silently failing:
die $err if $err;
Fix arguments to get_request
Your invocation of the get_request method looks wrong. According to the docs, you should be calling it like this:
my $response = $session->get_request(-varbindlist => [ $oid ]);
Note that Net::SNMP only works with numeric OIDs, so you'll have to change sysUpTime.0 to 1.3.6.1.2.1.1.3.0.
Looking at your script I noticed that hostname value has 10.0.1.202
but the snmpget command you're using has 10.0.1.203
wrong IP by any chance?
I would like to move several one liners into a single script.
For example:
perl -i.bak -pE "s/String_ABC/String_XYZ/g" Cities.Txt
perl -i.bak -pE "s/Manhattan/New_England/g" Cities.Txt
Above works well for me but at the expense of two disk I/O operations.
I would like to move the aforementioned logic into a single script so that all substitutions are effectuated with the file opened and edited only once.
EDIT1: Based on your recommendations, I wrote this snippet in a script which when invoked from a windows batch file simply hangs:
#!/usr/bin/perl -i.bak -p Cities.Txt
use strict;
use warnings;
while( <> ){
s/String_ABC/String_XYZ/g;
s/Manhattan/New_England/g;
print;
}
EDIT2: OK, so here is how I implemented your recommendation. Works like a charm!
Batch file:
perl -i.bal MyScript.pl Cities.Txt
MyScript.pl
#!/usr/bin/perl
use strict;
use warnings;
while( <> ){
s/String_ABC/String_XYZ/g;
s/Manhattan/New_England/g;
print;
}
Thanks a lot to everyone that contributed.
The -p wraps the argument to -E with:
while( <> ) {
# argument to -E
print;
}
So, take all the arguments to -E and put them in the while:
while( <> ) {
s/String_ABC/String_XYZ/g;
s/Manhattan/New_England/g;
print;
}
The -i sets the $^I variable, which turns on some special magic handling ARGV:
$^I = "bak";
The -E turns on the new features for that versions of Perl. You can do that by just specifying the version:
use v5.10;
However, you don't use anything loaded with that, at least in what you've shown us.
If you want to see everything a one-liner does, put a -MO=Deparse in there:
% perl -MO=Deparse -i.bak -pE "s/Manhattan/New_England/g" Cities.Txt
BEGIN { $^I = ".bak"; }
BEGIN {
$^H{'feature_unicode'} = q(1);
$^H{'feature_say'} = q(1);
$^H{'feature_state'} = q(1);
$^H{'feature_switch'} = q(1);
}
LINE: while (defined($_ = <ARGV>)) {
s/Manhattan/New_England/g;
}
continue {
die "-p destination: $!\n" unless print $_;
}
-e syntax OK
You can put arguments on the #! line. Perl will read them, even on Windows.
#!/usr/bin/perl -i.bak -p
s/String_ABC/String_XYZ/g;
s/Manhattan/New_England/g;
or you can keep it a one-liner as #ephemient said in the comments.
perl -i.bak -pE "s/String_ABC/String_XYZ/g; s/Manhattan/New_England/g" Cities.Txt
-i + -p basically puts a while loop around your program. Each line comes in as $_, your code runs, and $_ is printed out at the end. Repeat. So you can have as many statements as you want.
I am running my tests using TAP::Harness , when I run the tests from command line on a Linux system I get the test results on STDOUT as it is run but when i try to capture the output to a file as well as STDOUT using perl harness.pl | tee out.tap the results are buffered and displayed only at the end, I tried passing in a file handle to the new but the results are still buffered before being written to a file , Is there a way not to buffer the output, I have a long running suite and would like to look at the results while the tests are running as well as capture the output.
TAP::Harness version 3.22 and perl version 5.8.8
here is the sample code
harness.pl
#!/usr/bin/perl
use strict;
use warnings;
use TAP::Harness;
$|++;
my #tests = ('del.t',);
my $harness = TAP::Harness->new( {
verbosity => 1,
} );
$harness->runtests(#tests);
and the test del.t
use Test::More qw /no_plan/;
$|++;
my $count =1;
for (1 ..20 ) {
ok ( $count ++ == $_, "Pass $_");
sleep 1 if ( $count % 5 == 0 ) ;
}
Using script instead of tee does what you want:
script -c 'perl harness.pl' file
Found a simple change to make tee work as well: Specify a formatter_class:
my $harness = TAP::Harness->new( {
verbosity => 1,
formatter_class => 'TAP::Formatter::Console',
} );
This is because TAP::Harness normally uses a different default one if the output is not a tty, which is what is causing the buffering you're seeing.