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I basically want to check the incoming 'From' in the email received and then either
Keep it and make it deliver to the intended mailbox if the email matches a Specified MySQL/PostgreSQL
Database User (eg. select email from users where exists ('from email address') )
If the 'From' address is blank or it is not found in the database, the email should be discarded
Any way I can achieve this before the e-mail is delivered to the intended mailbox?
I am using Procmail + Virtualmin + Webmin + PostgreSQL
PS: I want to apply this filter not to the wole server but to some specified mailboxes/users (i'm assuming 1 user = 1 mailbox here)
Procmail can easily run an external command in a condition and react to its exit status. How exactly to make your particular SQL client set its exit code will depend on which one you are using; perhaps its man page will reveal an option to make it exit with an error when a query produces an empty result set, for example? Or else write a shell wrapper to look for empty output.
A complication is that Procmail (or rather, the companion utility formail) can easily extract a string from e.g. the From: header; but you want to reduce this to just the email terminus. This is a common enough task that it's easy to find a canned solution - generate a reply and then extract the To: address (sic!) from that.
FROM=`formail -rtzxTo:`
:0
* FROM ?? ^(one#example\.com|two#site\.example\.net|third#example\.org)$
{
:0
* ? yoursql --no-headers --fail-if-empty-result \
--batch --query databasename \
--eval "select yada yada where address = '$FROM'"
{ }
:0E
/dev/null
}
The first condition examines the variable and succeeds if it contains one of the addresses (my original answer simply had the regex . which matches if the string contains at least one character, any character; I'm not convinced this is actually necessary or useful; there should be no way for From: to be empty). If it is true, Procmail enters the braces; if not, they will be skipped.
The first recipe inside the braces runs an external command and examines its exit code. I'm imagining your SQL client is called yoursql and that it has options to turn off human-friendly formatting (table headers etc) and for running a query directly from the command line on a specific database. We use double quotes so that the shell will interpolate the variable FROM before running this command (maybe there is a safer way to pass string variables which might contain SQL injection attempts with something like --variable from="$FROM" and then use that variable in the query? See below.)
If there is no option to directly set the exit code, but you can make sure standard output is completely empty in the case of no result, piping the command to grep -q . will produce the correct exit code. In a more complex case, maybe write a simple Awk script to identify an empty result set and set its exit status accordingly.
Scraping together information from
https://www.postgresql.org/docs/current/app-psql.html,
How do you use script variables in psql?,
Making an empty output from psql,
and from your question, I end up with the following attempt to implement this in psql; but as I don't have a Postgres instance to test with, or any information about your database schema, this is still approximate at best.
* ? psql --no-align --tuples-only --quiet \
--dbname=databasename --username=something --no-password \
--variable=from="$FROM" \
--command="select email from users where email = :'from'" \
| grep -q .
(We still can't use single quotes around the SQL query, to completely protect it from the shell, because Postgres insists on single quotes around :'from', and the shell offers no facility for embedding literal single quotes inside single quotes.)
The surrounding Procmail code should be reasonably self-explanatory, but here goes anyway. In the first recipe inside the braces, if the condition is true, the empty braces in its action line are a no-op; the E flag on the next recipe is a condition which is true only if any of the conditions on the previous recipe failed. This is a common idiom to avoid having to use a lot of negations; perhaps look up "de Morgan's law". The net result is that we discard the message by delivering it to /dev/null if either condition in the first recipe failed; and otherwise, we simply pass it through, and Procmail will eventually deliver it to its default destination.
The recipe was refactored in response to updates to your question; perhaps now it would make more sense to just negate the exit code from psql with a ! in front:
FROM=`formail -rtzxTo:`
:0
* FROM ?? ^(one#example\.com|two#site\.example\.net|third#example\.org)$
* ! ? psql --no-align --tuples-only --quiet \
--dbname=databasename --username=something --no-password \
--variable=from="$FROM" \
--command="select email from users where email = :'from'" \
| grep -q .
/dev/null
Tangentially, perhaps notice how Procmail's syntax exploits the fact that a leading ? or a doubled ?? are not valid in regular expressions. So the parser can unambiguously tell that these conditions are not regular expressions; they compare a variable to the regex after ??, or examine the exit status of an external command, respectively. There are a few other special conditions like this in Procmail; arguably, all of them are rather obscure.
Newcomers to shell scripting should also notice that each shell command pipeline has two distinct results: whatever is being printed on standard output, and, completely separate from that, an exit code which reveals whether or not the command completed successfully. (Conventionally, a zero exit status signals success, and anything else is an error. For example, the exit status from grep is 0 if it finds at least one match, 1 if it doesn't, and usually some other nonzero exit code if you passed in an invalid regular expression, or you don't have permission to read the input file, etc.)
For further details, perhaps see also http://www.iki.fi/era/procmail/ which has an old "mini-FAQ" which covers several of the topics here, and a "quick reference" for looking up details of the syntax.
I'm not familiar with Virtualmin but https://docs.virtualmin.com/Webmin/PostgreSQL_Database_Server shows how to set up Postgres and as per https://docs.virtualmin.com/Webmin/Procmail_Mail_Filter I guess you will want to use the option to put this code in an include file.
I have an arithemic operation between two big value as following :
#!/bin/sh
a=$((0x1000000*0x0001d2))
echo $a
# result: -771751936
# wrong may the root cause is the size of variable
Have any solution to fix that?
NOTE: I'm using a very limited shell (sh).
-- Edit : Resolved. See answer.
Background:
I'm writing a shell that will perform some extra actions required on our system when someone resizes a database.
The shell is written in ksh (requirement), the OS is Solaris 5.10 .
The problem is with one of the checks, which verifies there's enough free space on the underlying OS.
Problem:
The check reads the df -k line for root, which is what I check in this step, and prints it to a file. I then "read" the contents into variables which I use in calculations.
Unfortunately, when I try to run an arithmetic operation on one of the variables, I get an error indicating it is null. And a debug output line I've placed after that line verifies that it is null... It lost it's value...
I've tried every method of doing this I could find online, they work when I run it manually, but not inside the shell file.
(* The file does have #!/usr/bin/ksh)
Code:
df -k | grep "rpool/ROOT" > dftest.out
RPOOL_NAME=""; declare -i TOTAL_SIZE=0; USED_SPACE=0; AVAILABLE_SPACE=0; AVAILABLE_PERCENT=0; RSIGN=""
read RPOOL_NAME TOTAL_SIZE USED_SPACE AVAILABLE_SPACE AVAILABLE_PERCENT RSIGN < dftest.out
\rm dftest.out
echo $RPOOL_NAME $TOTAL_SIZE $USED_SPACE $AVAILABLE_SPACE $AVAILABLE_PERCENT $RSIGN
((TOTAL_SIZE=$TOTAL_SIZE/1024))
This is the result:
DBResize.sh[11]: TOTAL_SIZE=/1024: syntax error
I'm pulling hairs at this point, any help would be appreciated.
The code you posted cannot produce the output you posted. Most obviously, the error is signalled at line 11 but you posted fewer than 11 lines of code. The previous lines may matter. Always post complete code when you ask for help.
More concretely, the declare command doesn't exist in ksh, it's a bash thing. You can achieve the same result with typeset (declare is a bash equivalent to typeset, but not all options are the same). Either you're executing this script with bash, or there's another error message about declare, or you've defined some additional commands including declare which may change the behavior of this code.
None of this should have an impact on the particular problem that you're posting about, however. The variables created by read remain assigned until the end of the subshell, i.e. until the code hits a ), the end of a pipe (left-hand side of the pipe only in ksh), etc.
About the use of declare or typeset, note that you're only declaring TOTAL_SIZE as an integer. For the other variables, you're just assigning a value which happens to consist exclusively of digits. It doesn't matter for the code you posted, but it's probably not what you meant.
One thing that may be happening is that grep matches nothing, and therefore read reads an empty line. You should check for errors. Use set -e in scripts to exit at the first error. (There are cases where set -e doesn't catch errors, but it's a good start.)
Another thing that may be happening is that df is splitting its output onto multiple lines because the first column containing the filesystem name is too large. To prevent this splitting, pass the option -P.
Using a temporary file is fragile: the code may be executed in a read-only directory, another process may want to access the same file at the same time... Here a temporary file is useless. Just pipe directly into read. In ksh (unlike most other sh variants including bash), the right-hand side of a pipe runs in the main shell, so assignments to variables in the right-hand side of a pipe remain available in the following commands.
It doesn't matter in this particular script, but you can use a variable without $ in an arithmetic expression. Using $ substitutes a string which can have confusing results, e.g. a='1+2'; $((a*3)) expands to 7. Not using $ uses the numerical value (in ksh, a='1+2'; $((a*3)) expands to 9; in some sh implementations you get an error because a's value is not numeric).
#!/usr/bin/ksh
set -e
typeset -i TOTAL_SIZE=0 USED_SPACE=0 AVAILABLE_SPACE=0 AVAILABLE_PERCENT=0
df -Pk | grep "rpool/ROOT" | read RPOOL_NAME TOTAL_SIZE USED_SPACE AVAILABLE_SPACE AVAILABLE_PERCENT RSIGN
echo $RPOOL_NAME $TOTAL_SIZE $USED_SPACE $AVAILABLE_SPACE $AVAILABLE_PERCENT $RSIGN
((TOTAL_SIZE=TOTAL_SIZE/1024))
Strange...when I get rid of your "declare" line, your original code seems to work perfectly well (at least with ksh on Linux)
The code :
#!/bin/ksh
df -k | grep "/home" > dftest.out
read RPOOL_NAME TOTAL_SIZE USED_SPACE AVAILABLE_SPACE AVAILABLE_PERCENT RSIGN < dftest.out
\rm dftest.out
echo $RPOOL_NAME $TOTAL_SIZE $USED_SPACE $AVAILABLE_SPACE $AVAILABLE_PERCENT $RSIGN
((TOTAL_SIZE=$TOTAL_SIZE/1024))
print $TOTAL_SIZE
The result :
32962416 5732492 25552588 19% /home
5598
Which are the value a simple df -k is returning. The variables seem to last.
For those interested, I have figured out that it is not possible to use "read" the way I was using it.
The variable values assigned by "read" simply "do not last".
To remedy this, I have applied the less than ideal solution of using the standard "while read" format, and inside the loop, echo selected variables into a variable file.
Once said file was created, I just "loaded" it.
(pseudo code:)
LOOP START
echo "VAR_A="$VAR_A"; VAR_B="$VAR_B";" > somefile.out
LOOP END
. somefile.out
I'm trying to set up a simple backup process for a folder on my C drive that will back that folder up to another location on the network. I know how to create a scheduled task but I'm struggling to understand why my command prompt code won't work - I'm a novice when it comes to the Command Prompt though!
So my question is two fold:
Why does echo %variableName% not return the variable value - it only returns %variableName%.
This is what I type in:
#echo off
set varA = 5
echo %varA%
%varA% <- This is what its popping out
Do I need different preceeding and succeeding characters for this?
I want to create a folder with the date for the name (I do realize that are quite a few questions out there on this but they didn't work), how do I do it?
Here is what I tried:
set folder_name = %DATE:/=_%
set folder_name <- Display value for folder_name
folder_name = Wed 11_06_2013 <- Actual value
When I try to do this:
mkdir %folder_name%
dir
Creates a folder with this %_date% as the name.
Where am I going wrong?
Thanks
Space is significant in SET statements.
SET varspace=spacevalue
will set a variable named "varspace" to "spacevalue"
Remove the spaces and it should be plain sailing...
Oh - except that if the variable contains a space, then commands such as MD or mkdir (which are synonyms) require "rabbits ears" around the value, thus:
mkdir "%folder_name%"
I am trying to create my first zsh completion script, in this case for the command netcfg.
Lame as it may sound I have stuck on the first hurdle, disclaimer, I know how to do this crudely, however I seek the "ZSH WAY" to do this.
I need to list the files in /etc/networking but only the files, not the directory component, so I do the following.
echo $(ls /etc/network.d/*(.))
/etc/network.d/ethernet-dhcp /etc/network.d/wireless-wpa-config
What I wanted was:
ethernet-dhcp wireless-wpa-config
So I try (excuse my naivity) :
echo ${(s/*\/)$(ls /etc/network.d/*(.))}
/etc/network.d/ethernet-dhcp /etc/network.d/wireless-wpa-config
It seems that this doesn't work, I'm sure there must be some clever way of doing this by splitting into an array and getting the last part but as I say, I'm complete noob at this.
Any advice gratefully received.
General note: There is no need to use ls to generate the filenames. You might as well use echo some*glob. But if you want to protect the possible embedded newline characters even that is a bad idea. The first example below globs directly into an array to protect embedded newlines. The second one uses printf to generate NUL terminated data to accomplish the same thing without using a variable.
It is easy to do if you are willing to use a variable:
typeset -a entries
entries=(/etc/network.d/*(.)) # generate the list
echo ${entries#/etc/network.d/} # strip the prefix from each one
You can also do it without a variable, but the extra stuff to isolate individual entries is a bit ugly:
# From the inside, to the outside:
# * glob the entries
# * NUL terminate them into a single string
# * split at NUL
# * strip the prefix from each one
echo ${${(0)"$(printf '%s\0' /etc/network.d/*(.))"}#/etc/network.d/}
Or, if you are going to use a subshell anyway (i.e. the command substitution in the previous example), just cd to the directory so it is not part of the glob expansion (plus, you do not have to repeat the directory name):
echo ${(0)"$(cd /etc/network.d && printf '%s\0' *(.))"}
Chris Johnsen's answer is full of useful information about zsh, however it doesn't mention the much simpler solution that works in this particular case:
echo /etc/network.d/*(:t)
This is using the t history modifier as a glob qualifier.
Thanks for your suggestions guys, having done yet more reading of ZSH and coming back to the problem a couple of days later, I think I've got a very terse solution which I would like to share for your benefit.
echo ${$(print /etc/network.d/*(.)):t}
I'm used to seeing basename(1) stripping off directory components; also, you can use echo /etc/network/* to get the file listing without running the external ls program. (Running external programs can slow down completion more than you'd like; I didn't find a zsh-builtin for basename, but that doesn't mean that there isn't one.)
Here's something I hope will help:
haig% for f in /etc/network/* ; do basename $f ; done
if-down.d
if-post-down.d
if-pre-up.d
if-up.d
interfaces