I'm currently having a already a bash script with a few thousand lines which sends various queries MySQL to generate applicable output for munin.
Up until now the results were simply numbers which weren't a problem, but now I'm facing a challenge to work with a more complex query in the form of:
$ echo "SELECT id, name FROM type ORDER BY sort" | mysql test
id name
2 Name1
1 Name2
3 Name3
From this result I need to store the id and name (and their respective association) and based on the IDs need to perform further queries, e.g. SELECT COUNT(*) FROM somedata WHERE type = 2 and later output that result paired with the associated name column from the first result.
I'd know easily how to do it in PHP/Ruby , but I'd like to spare to fork another process especially since it's polled regularly, but I'm complete lost where to start with bash.
Maybe using bash is the wrong approach anyway and I should just fork out?
I'm using GNU bash, version 3.2.39(1)-release (i486-pc-linux-gnu).
My example is not Bash, but I'd like to point out my parameters at invoking the mysql command, they surpress the boxing and the headers.
#!/bin/sh
mysql dbname -B -N -s -e "SELECT * FROM tbl" | while read -r line
do
echo "$line" | cut -f1 # outputs col #1
echo "$line" | cut -f2 # outputs col #2
echo "$line" | cut -f3 # outputs col #3
done
You would use a while read loop to process the output of that command.
echo "SELECT id, name FROM type ORDER BY sort" | mysql test | while read -r line
do
# you could use an if statement to skip the header line
do_something "$line"
done
or store it in an array:
while read -r line
do
array+=("$line")
done < <(echo "SELECT id, name FROM type ORDER BY sort" | mysql test)
That's a general overview of the technique. If you have more specific questions post them separately or if they're very simple post them in a comment or as an edit to your original question.
You're going to "fork out," as you put it, to the mysql command line client program anyhow. So either way you're going to have process-creation overhead. With your approach of using a new invocation of mysql for each query you're also going to incur the cost of connecting to and authenticating to the mysqld server multiple times. That's expensive, but the expense may not matter if this app doesn't scale up.
Making it secure against sql injection is another matter. If you prompt a user for her name and she answers "sally;drop table type;" she's laughing and you're screwed.
You might be wise to use a language that's more expressive in the areas that are important for data-base access for some of your logic. Ruby, PHP, PERL are all good choices. PERL happens to be tuned and designed to run snappily under shell script control.
Related
i'm translating a bash script to a Lua program. In bash script there is a line:
mapfile -t vol < <( cat csv_file | head -$id | grep locateme | tail -3 | cut -f6 -d\,)
the result of that is:
vol[0]=22
vol[1]=33
vol[2]=44
the csv_file is like:
16,a,b,c,d,9,16,0,3,65,0,0,locateme
16,a,b,c,d,11,16,0,3,65,0,0,notme
16,a,b,c,d,22,16,0,3,65,0,0,locateme
16,a,b,c,d,33,16,0,3,65,0,0,locateme
16,a,b,c,d,32,16,0,3,65,0,0,notme
16,a,b,c,d,44,16,0,3,65,0,0,locateme
I need a table with the same results than bash:
vol[1]=22
vol[2]=33
vol[3]=44
please, i have no idea how to start with this
Instead of a Bash array you're going to use a Lua table.
local vol = {}
You'll need a generic for loop and the file:lines(...) iterator. It is a good idea to read through the whole io library.
This will allow you to get each line of the csv file as a string for further processing.
No you'll need Lua's string library. There are multiple ways to do this. One option is to use another generic for loop with string.gmatch and a suitable string pattern that captures the value you're interested in.
I am trying to update a simple JSON file (consists of one object with several key/value pairs) and I am using the same command yet getting different results (sometimes even having the whole json wiped with the 2nd command). The command I am trying is:
cat ~/Desktop/config.json | jq '.Option = "klay 10"' | tee ~/Desktop/config.json
This command perfectly replaces the value of the minerOptions key with "klay 10", my intended output.
Then, I try to run the same process on the newly updated file (just value is changed for that one key) and only get interactive terminal with no result. ps unfortunately isn't helpful in showing what's going on. This is what I do after getting that first command to perfectly change the value of the key:
cat ~/Desktop/config.json | jq ‘.othOptions = "-epool etc-eu1.nanopool.org:14324 -ewal 0xc63c1e59c54ca935bd491ac68fe9a7f1139bdbc0 -mode 1"' | tee ~/Desktop/config.json
which I would have expected would replace the othOptions key value with the assigned result, just as the last did. I tried directly sending the stdout to the file, but no result there either. I even tried piping one more time and creating a temp file and then moving it to change to original, all of these, as opposed to the same identical command, just return > and absolutely zero output; when I quit the process, it is the same value as before, not the new one.
What am I missing here that is causing the same command with just different inputs (the key in second comes right after first and has identical structure, it's not creating an object or anything, just key-val pair like first. I thought it could be tee but any other implementation like a passing of stdout to file produces the same constant > waiting for a command, no user.
I genuinely looked everywhere I could online for why this could be happening before resorting to SE, it's giving me such a headache for what I thought should be simple.
As #GordonDavisson pointed out, using tee to overwrite the input file is a (well-known - see e.g. the jq FAQ) recipe for disaster. If you absolutely positively want to overwrite the file unconditionally, then you might want to consider using sponge, as in
jq ... config.json | sponge config.json
or more safely:
cp -p config.json config.json.bak && jq ... config.json | sponge config.json
For further details about this and other options, search for ‘sponge’ in the FAQ.
This should be an incredibly easy question but I am not very familiar with bash and I am taking way longer than I should to figure it out.
declare -a ids=( 1 2 3 )
for i in "${ids[#]}";
do
re= $(mysql -h .... "SELECT col_A FROM DBA WHERE id=$i")
if [ $re -eq 0 ]; then
echo sucess
fi
done
This is an example of what I am trying to do, I have an id array and I want to send a query to my db so I can get a flag in the row with a certain id and then do something based on that. But I keep getting unexpected token errors and I am not entirely sure why
Edit: While copying the code and deleting some private information somehow I deleted the then, it was present in the code I was testing.
Based on what you described and the partial script, I am not certain I can completely create what you are trying to do but the token error messages you are experiencing usually have to do with the way bash handles whitespace as a delimiter. A few comments based on what you posted:
You need to remove the space around the equal sign in declaring an variable, so the space after the equal sign in re= needs to removed.
Because bash will is sensitive to whitespace, you need to quote variables declarations that might contain a space. To be safe, quotes need to be around the sub-shell $( )
You were missing the then in the if statement
It is important that variables in the test brackets, that is single [ ]s, must be quoted. Using an unquoted string with -eq, or even just the unquoted string alone within test brackets normally works, however, this is an unsafe practice and can give unpredictable results.
So, taking into account the items noted, the updated script would look something like:
declare -a ids=( 1 2 3 )
for i in "${ids[#]}";
do
re="$(mysql -h .... "SELECT col_A FROM DBA WHERE id=$i")"
if [ "$re" -eq "0" ]; then
echo "success"
fi
done
Can you try working the edits mentioned into your script and see if you are able to get it working? Remember, it will be helpful for you to use a site like ShellCheck to learn more about potential pitfalls or the uniquenesses of bash syntax. This will help to ensure you are working toward a solution to your specific need rather then getting trapped by some tricky syntax.
After you have worked through those edits, can you report back your experience?
EDIT
Based on your comments there is a good chance you are not running your script with bash despite the including #!/bin/bash at the top of your script. When you run the script as sh scriptname.sh you are forcing the script to be run by sh not bash. Try running your script like this /bin/bash scriptname.sh then report back on your experience.
For more information on the differences between various shells, see Unix/Linux : Difference between sh , csh , ksh and bash Shell
Your problem with your if statement is that you do not have the then keyword. A simple fix is:
declare -a ids=( 1 2 3 )
for i in "${ids[#]}";
do
re= $(mysql -h .... "SELECT col_A FROM DBA WHERE id=$i")
if [ $re -eq 0 ]; then
echo sucess
fi
done
Also here is a great reference on if statements in bash
I'm creating a Bash script to parse the air pollution levels from the webpage:
http://aqicn.org/city/beijing/m/
There is a lot of stuff in the file, but this is the relevant bit:
"iaqi":[{"p":"pm25","v":[59,21,112],"i":"Beijing pm25 (fine
particulate matter) measured by U.S Embassy Beijing Air Quality
Monitor
(\u7f8e\u56fd\u9a7b\u5317\u4eac\u5927\u4f7f\u9986\u7a7a\u6c14\u8d28\u91cf\u76d1\u6d4b).
Values are converted from \u00b5g/m3 to AQI levels using the EPA
standard."},{"p":"pm10","v":[15,5,69],"i":"Beijing pm10
(respirable particulate matter) measured by Beijing Environmental
Protection Monitoring Center
I want the script to parse and display 2 numbers: current PM2.5 and PM10 levels (the numbers in bold in the above paragraph).
CITY="beijing"
AQIDATA=$(wget -q 0 http://aqicn.org/city/$CITY/m/ -O -)
PM25=$(awk -v FS="(\"p\":\"pm25\",\"v\":\\\[|,[0-9]+)" '{print $2}' <<< $AQIDATA)
PM100=$(awk -v FS="(\"p\":\"pm10\",\"v\":\\\[|,[0-9]+)" '{print $2}' <<< $AQIDATA)
echo $PM25 $PM100
Even though I can get PM2.5 levels to display correctly, I cannot get PM10 levels to display. I cannot understand why, because the strings are similar.
Anyone here able to explain?
The following approach is based on two steps:
(1) Extracting the relevant JSON;
(2) Extracting the relevant information from the JSON using a JSON-aware tool -- here jq.
(1) Ideally, the web service would provide a JSON API that would allow one to obtain the JSON directly, but as the URL you have is intended for viewing with a browser, some form of screen-scraping is needed. There is a certain amount of brittleness to such an approach, so here I'll just provide something that currently works:
wget -O - http://aqicn.org/city/beijing/m |
gawk 'BEGIN{RS="function"}
$1 ~/getAqiModel/ {
sub(/.*var model=/,"");
sub(/;return model;}/,"");
print}'
(gawk or an awk that supports multi-character RS can be used; if you have another awk, then first split on "function", using e.g.:
sed $'s/function/\\\n/g' # three backslashes )
The output of the above can be piped to the following jq command, which performs the filtering envisioned in (2) above.
(2)
jq -c '.iaqi | .[]
| select(.p? =="pm25" or .p? =="pm10") | [.p, .v[0]]'
The result:
["pm25",59]
["pm10",15]
I think your problem is that you have a single line HTML file that contains a script that contains a variable that contains the data you are looking for.
Your field delimiters are either "p":"pm100", "v":[ or a comma and some digits.
For pm25 this works, because it is the first, and there are no occurrences of ,21 or something similar before it.
However, for pm10, there are some that are associated with pm25 ahead of it. So the second field contains the empty string between ,21 and ,112
#karakfa has a hack that seems to work -- but he doesn't explain very well why it works.
What he does is use awk's record separator (which is usually a newline) and sets it to either of :, ,, or [. So in your case, one of the records would be "pm25", because it is preceded by a colon, which is a separator, and succeeded by a comma, also a separator.
Once it hits the matching content ("pm25") it sets a counter to 4. Then, for this and the next records, it counts this counter down. "pm25" itself, "v", the empty string between : and [, and finally reaches one when hitting the record with the number you want to output: 4 && ! 3 is false, 3 && ! 2 is false, 2 && ! 1 is false, but 1 && ! 0 is true. Since there is no execution block, awk simply prints this record, which is the value you want.
A more robust work would probably be using xpath to find the script, then use some json parser or similar to get the value.
chw21's helpful answer explains why your approach didn't work.
peak's helpful answer is the most robust, because it employs proper JSON parsing.
If you don't want to or can't use third-party utility jq for JSON parsing, I suggest using sed rather than awk, because awk is not a good fit for field-based parsing of this data.
$ sed -E 's/^.*"pm25"[^[]+\[([0-9]+).+"pm10"[^[]+\[([0-9]+).*$/\1 \2/' <<< "$AQIDATA"
59 15
The above should work with both GNU and BSD/OSX sed.
To read the result into variables:
read pm25 pm10 < \
<(sed -E 's/^.*"pm25"[^[]+\[([0-9]+).+"pm10"[^[]+\[([0-9]+).*$/\1 \2/' <<< "$AQIDATA")
Note how I've chosen lowercase variable names, because it's best to avoid all upper-case variables in shell programming, so as to avoid conflicts with special shell and environment variables.
If you can't rely on the order of the values in the source string, use two separate sed commands:
pm25=$(sed -E 's/^.*"pm25"[^[]+\[([0-9]+).*$/\1/' <<< "$AQIDATA")
pm10=$(sed -E 's/^.*"pm10"[^[]+\[([0-9]+).*$/\1/' <<< "$AQIDATA")
awk to the rescue!
If you have to, you can use this hacky way using smart counters with hand-crafted delimiters. Setting RS instead of FS transfers looping through fields to awk itself. Multi-char RS is not available for all awks (gawk supports it).
$ awk -v RS='[:,[]' '$0=="\"pm25\""{c=4} c&&!--c' file
59
$ awk -v RS='[:,[]' '$0=="\"pm10\""{c=4} c&&!--c' file
15
Morning/Evening all,
I've got a problem where I'm making a script for work that uses ClamAV to scan for malware, and then place it's results in MySQL by taking the resultant ClamAV logs using grep with awk to convert the right parts of the log to a variable. The problem I have is that whilst I have done the summary ok, the syntax of detections makes it slightly more difficult. I'm no expert at regex by all means and this is a bit of a learning experience, so there is probably a far better way of doing it than I have!
The lines I'm trying to parse looks like these:
/net/nas/vol0/home/recep/SG4rt.exe: Worm.SomeFool.P FOUND
/net/nas/vol0/home/recep/SG4rt.exe: moved to '/srv/clamav/quarantine/SG4rt.exe'
As far as I was able to establish, I need a positive lookbehind to match what happens after and before the colon, without actually matching the colon or the space after it, and I can't see a clear way of doing it from RegExr without it thinking I'm trying to look for two colons. To make matters worse, we sometimes get these too...
WARNING: Can't open file /net/nas/vol0/home/laser/samples/sample1.avi: Permission denied
The end result is that I can build a MySQL query that inserts the path, malware found and where it was moved to or if there was an error then the path, then the error encountered so as to convert each element to a variable contents in a while statement.
I've done the scan summary as follows:
Summary looks like:
----------- SCAN SUMMARY -----------
Known viruses: 329
Engine version: 0.97.1
Scanned directories: 17350
Scanned files: 50342
Infected files: 3
Total errors: 1
Data scanned: 15551.73 MB
Data read: 16382.67 MB (ratio 0.95:1)
Time: 3765.236 sec (62 m 45 s)
Parsing like this:
SCANNED_DIRS=$(cat /srv/clamav/$IY-scan-$LOGTIME.log | grep "Scanned directories" | awk '{gsub("Scanned directories: ", "");print}')
SCANNED_FILES=$(cat /srv/clamav/$IY-scan-$LOGTIME.log | grep "Scanned files" | awk '{gsub("Scanned files: ", "");print}')
INFECTED=$(cat /srv/clamav/$IY-scan-$LOGTIME.log | grep "Infected files" | awk '{gsub("Infected files: ", "");print}')
DATA_SCANNED=$(cat /srv/clamav/$IY-scan-$LOGTIME.log | grep "Data scanned" | awk '{gsub("Data scanned: ", "");print}')
DATA_READ=$(cat /srv/clamav/$IY-scan-$LOGTIME.log | grep "Data read" | awk '{gsub("Data read: ", "");print}')
TIME_TAKEN=$(cat /srv/clamav/$IY-scan-$LOGTIME.log | grep "Time" | awk '{gsub("Time: ", "");print}')
END_TIME=$(date +%s)
mysql -u scanner_parser --password=removed sc_live -e "INSERT INTO bs.live.bs_jobstat VALUES (NULL, '$CURRTIME', '$PID', '$IY', '$SCANNED_DIRS', '$SCANNED_FILES', '$INFECTED', '$DATA_SCANNED', '$DATA_READ', '$TIME_TAKEN', '$END_TIME');"
rm -f /srv/clamav/$IY-scan-$LOGTIME.log
Some of those variables are from other parts of the script and can be ignored. The reason I'm doing this is to save logfile clutter and have a simple web based overview of the status of the system.
Any clues? Am I going about all this the wrong way? Thanks for help in advance, I do appreciate it!
From what I can determine from the question, it seems like you are asking how to distinguish the lines you want from the logger lines that start with WARNING, ERROR, INFO.
You can do this without getting to fancy with lookahead or lookbehind. Just grep for lines beginning with
"/net/nas/vol0/home/recep/SG4rt.exe: "
then using awk you can extract the remainder of the line. Or you can gsub the prefix out like you are doing in the summary processing section.
As far as the question about processing the summary goes, what strikes me most is that you are processing the entire file multiple times, each time pulling out one kind of line. For tasks like this, I would use Perl, Ruby, or Python and make one pass through the file, collecting the pieces of each line after the colon, storing them in regular programming language variables (not env variables), and forming the MySQL insert string using interpolation.
Bash is great for some things but IMHO you are justified in using a more general scripting language (Perl, Python, Ruby come to mind).