here is what I want to do
while ["ps a | grep '[m]ono' | awk '{print $1}'" != ""] ; do
kill ps a | grep '[m]ono' | awk '{print $1}'
done
meaning if the grep returns nothing, don't try a kill.
The thing is I've always been lost with the expression evaluation in bash, sometime I use " " around something, sometime it's eval, sometime it's ''.
Could someone explain to me how to write the condition in my loop and explain the difference between the above? I'm used to find the working one with many tries and it feels like a huge loss of time.
Best choice: Do something else.
Utilities already exist for this purpose. Example:
killall mono
pkill mono
...or, even better, something targeted to the specific executable you want to terminate:
fuser -k /path/to/something.exe
...which would kill only programs with a file handle on that specific executable, rather than all applications running with mono on the machine.
...but, to explain the bugs:
There are two things wrong here: Missing command substitutions, and missing whitespace.
Missing whitespace:
["ps a | grep '[m]ono' | awk '{print $1}'" != ""]
...is literally trying to run a command with a name starting with [ps, as in, looking in the PATH for...
/bin/[ps\ a
/usr/bin/[ps\ a
...etc. [ is a command, and needs a space after its name like any other command. Thus:
[ "ps a | grep '[m]ono' | awk '{print $1}'" != "" ]
...fixes this problem (but leaves another one).
Missing command substitutions:
[ "ps a | grep '[m]ono' | awk '{print $1}'" != "" ]
...is comparing a string that starts with "ps a" to to ""; it does not compare the output of running a command that starts with ps a. To do that, you'd instead run:
[ "$(ps a | grep '[m]ono' | awk '{print $1}')" != "" ]
The content of $(...) is replaced with the output of the command within; thus, running your pipeline and comparing its output to an empty string.
Related
I am trying to execute the one liner below as a part of bash script.
command1 |grep -ID|grep -v + | awk '{print "command2" $2}'|bash
The first part of the pipe prints the info below:
root#system:~# command1 |grep -v ID|grep -v +
| id | name | mac_address | fixed_ips |
| 00277225-34fa-48f5-9a2a-ee5f1c5b1dcb | dummy | fa:18:3e:c4:85:94 | {"subnet_id": "0cd4d824-4420-4049-87c3-ed33c3addbf5", "ip_address": "11.170.1.121"} |
:
:
| ff9a6ed5-9694-45bc-bf71-59565f96d809 | BAT-T0-A2-0-7-tport | fa:18:3e:62:70:fb | {"subnet_id": "f9ae81ed-3b1a-45a7-96fd-c417ed32
So, $2 in awk command2 is "00277225-34fa-48f5-9a2a-ee5f1c5b1dcb".
e.g.
command2 00277225-34fa-48f5-9a2a-ee5f1c5b1dcb
The whole purpose of this one-liner is to execute a number of "command2" instances with different parameter values from the printout above.
e.g.
command2 00277225-34fa-48f5-9a2a-ee5f1c5b1dcb
command2 ff9a6ed5-9694-45bc-bf71-59565f96d809
:
:
But I can not make the $2 recognized the way below
command1 |grep -ID|grep -v + | awk '{print "command2" $2}'|bash
I think I am missing few syntax tricks here (as newbie).
p.s: If I copy / paste the whole line in command line, it works fine.
You seem to be looking for
command1 | awk '!/ID/ && !/\+/ {print $2}' | xargs -n 1 command2
I refactored the ugly useless greps into the Awk script; but the real beef here is xargs. It reads parameters from standard input and passes them on to the command you supply in the positional parameters.
The option -n 1 says to only accept one additional argument at a time; but if command2 is a well-written standard Unix command, it can probably accept an arbitrary number of arguments, and will simply loop over them. In that case, removing -n 1 will be a lot more efficient.
Incidentally, your original attempt was fairly close; you should have added a space after command2 in the print statement. But I hope this solution will also help you see how to "think Unix".
Consider the following on a debian based system:
VAR=$(dpkg --get-selections | awk '{print $1}' | grep linux-image)
This will print a list of installed packages with the string "linux-image" in them on my system this output looks like:
linux-image-3.11.0-17-generic
linux-image-extra-3.11.0-17-generic
linux-image-generic
Now as we all know
echo $VAR
results in
linux-image-3.11.0-17-generic linux-image-extra-3.11.0-17-generic linux-image-generic
and
echo "$VAR"
results in
linux-image-3.11.0-17-generic
linux-image-extra-3.11.0-17-generic
linux-image-generic
I do not want to use external commands in a if clause, it seems rather dirty and not very elegant, so I wanted to use bash built in regex matching:
if [[ "$VAR" =~ ^linux-image-g ]]; then
echo "yes"
fi
however that does not work, since it does not seem to consider multiple lines here. How can I match beginnings of lines in a variable?
There's nothing wrong with using an external command as part of the if statement; I would skip the VAR variable altogether and use
if dpkg --get-selections | awk '{print $1}' | grep -q linux-image;
The -q option to grep suppresses its output, and the if statement uses the exit status of grep directly. You could also drop the grep and test $1 directly in the awk script:
if dpkg --get-selections | awk '$1 =~ "^linux-image" { exit 0; } END {exit 1}'; then
or you can skip awk, since there doesn't seem to be a real need to drop the other fields before calling grep:
if dpkg --get-selections | grep -q '^linux-image'; then
This question already has answers here:
How do I set a variable to the output of a command in Bash?
(15 answers)
Closed 8 years ago.
I'm trying to write a simple script for killing a process. I've already read Find and kill a process in one line using bash and regex so please don't redirect me to that.
This is my code:
LINE=$(ps aux | grep '$1')
PROCESS=$LINE | awk '{print $2}'
echo $PROCESS
kill -9 $PROCESS
I want to be able to run something like
sh kill_proc.sh node and have it run
kill -9 node
But instead what I get is
kill_process.sh: line 2: User: command not found
I found out that when I log $PROCESS it is empty.
Does anyone know what I'm doing wrong?
PROCESS=$(echo "$LINE" | awk '{print $2}')
or
PROCESS=$(ps aux | grep "$1" | awk '{print $2}')
I don't know why you're getting the error you quoted. I can't reproduce it. When you say this:
PROCESS=$LINE | awk '{print $2}'
the shell expands it to something like this:
PROCESS='mayoff 10732 ...' | awk '{print $2}'
(I've shortened the value of $LINE to make the example readable.)
The first subcommand of the pipeline sets variable PROCESS; this variable-setting command has no output so awk reads EOF immediately and prints nothing. And since each subcommand of the pipeline runs in a subshell, the setting of PROCESS takes place only in a subshell, not in the parent shell running the script, so PROCESS is still not set for later commands in your script.
(Note that some versions of bash can run the last subcommand of the pipeline in the current shell instead of in a subshell, but that doesn't affect this example.)
Instead of setting PROCESS in a subshell and feeding nothing to awk on standard input, you want to feed the value of LINE to awk and store the result in PROCESS in the current shell. So you need to run a command that writes the value of LINE to its standard output, and connects that standard output to the standard input of awk. The echo command can do this (or the printf command, as chepner pointed out in his answer).
You need to use echo (or printf) to actually put the value of $LINE onto the standard input of the awk command.
LINE=$(ps aux | grep "$1")
PROCESS=$(echo "$LINE" | awk '{print $2}')
echo $PROCESS
kill -9 $PROCESS
There's no need use LINE; you can set PROCESS with a single line
PROCESS=$(ps aux | grep "$1" | awk '{print $2}')
or better, skip the grep:
PROCESS=$(ps aux | awk -v pname="$1" '$1 ~ pname {print $2}')
Finally, don't use kill -9; that's a last resort for debugging faulty programs. For any program that you didn't write yourself, kill "$PROCESS" should be sufficient.
I have tried all kinds of filters using grep to try and solve this but just cannot crack it.
cpumem="$(ps aux | grep -v 'grep' | grep 'firefox-bin' | awk '{printf $3 "\t" $4}'
I am extracting the CPU and Memory usage for a process and when I run it from the command line, I get the 2 fields outputted correctly:
ps aux | grep -v 'grep' | grep 'firefox-bin' | awk '{printf $3 "\t" $4}'
> 1.1 4.4
but the same command executed from within the bash script produces this:
cpumem="$(ps aux | grep -v 'grep' | grep 'firefox-bin' | awk '{printf $3 "\t" $4}')"
echo -e cpumem
> 1.1 4.40.0 0.10.0 0.0
I am guessing that it is picking up 3 records, but I just don't know where from.
I am filtering out any other grep processes by using grep -v 'grep', can someone offer any suggestions or a more reliable way ??
Maybe you have 3 records because 3 firefox are running (or one is running, and it is threading itself).
You can avoid the grep hazzle by giving ps and option to select the processes. E.g. the -C to select processes by name. With ps -C firefox-bin you get only the firefox processes. But this does not help at all, when there is more than one process.
(You can also use the ps option to output only the columns you want, so your line would be like
ps -C less --no-headers -o %cpu,%mem
).
For the triple-record you must come up with a solution, what should happen, where more than one is running. In a multiuser environment with programms that are threading there can always be situations where you have more than one process of a kind. There are many possible solution where none can help you, as you dont say, way you are going to do with it. One can think of solutions like selecting only from one user, and only the one with the lowest pid, or the process-leader in case of groups, to change the enclosing bash-script to use a loop to handle the multiple values or make it working somehow different when ps returns multiple results.
I was not able to reproduce the problem, but to help you debug, try print $11 in your awk command, that will tell you what process it is talking about
cpumem="$(ps aux | grep -v 'grep' | grep 'firefox-bin' | awk '{printf $3 "\t" $4 "\t" $11 "\n"}')"
echo -e cpumem
It's actually an easy fix for the output display; In your echo statement, wrap the variable in double-quotes:
echo -e "$cpumem"
Without using double-quotes, newlines are not preserved by converting them to single-spaces (or empty values). With quotes, the original text of the variable is preserved when outputted.
If your output contains multiple processes (i.e. - multiple lines), that means your grep actually matched multiple lines. There's a chance a child-process is running for firefox-bin, maybe a plugin/container? With ps aux, the 11th column will tell you what the actual process is, so you can update your awk to be the following (for debugging):
awk '{printf $3 "\t" $4 "\t" $11}'
I'm trying to create a shell script getting the process id of the Skype app on my Mac.
ps -clx | grep 'Skype' | awk '{print $2}' | head -1
The above is working fine, but there are two problems:
1)
The grep command would get all process if their name just contains "Skype". How can I ensure that it only get the result, if the process name is exactly Skype?
2)
I would like to make a shell script from this, which can be used from the terminal but the process name should be an argument of this script:
#!/bin/sh
ps -clx | grep '$1' | awk '{print $2}' | head -1
This isn't returning anything. I think this is because the $2 in the awk is treated as an argument too. How can I solve this?
Your ps -cl1 output looks like this:
UID PID PPID F CPU PRI NI SZ RSS WCHAN S ADDR TTY TIME CMD
501 185 172 104 0 31 0 2453272 1728 - S ffffff80145c5ec0 ?? 0:00.00 httpd
501 303 1 80004004 0 31 0 2456440 1656 - Ss ffffff8015131300 ?? 0:11.78 launchd
501 307 303 4004 0 33 0 2453456 7640 - S ffffff8015130a80 ?? 0:46.17 distnoted
501 323 303 40004004 0 33 0 2480640 9156 - S ffffff80145c4dc0 ?? 0:03.29 UserEventAgent
Thus, the last entry in each line is your command. That means you can use the full power of regular expressions to help you.
The $ in a regular expression means the end of the string, thus, you could use $ to specify that not only does the output must have Skype in it, it must end with Skype. This means if you have a command called Skype Controller, you won't pull it up:
ps -clx | grep 'Skype$' | awk '{print $2}' | head -1
You can also simplify things by using the ps -o format to just pull up the columns you want:
ps -eo pid,comm | grep 'Skype$' | awk '{print $1}' | head -1
And, you can eliminate head by simply using awk's ability to select your line for you. In awk, NR is your record number. Thus you could do this:
ps -eo pid,comm | grep 'Skype$' | awk 'NR == 1 {print $1}'
Heck, now that I think of it, we could eliminate the grep too:
ps -eo pid,comm | awk '/Skype$/ {print $1; exit}'
This is using awk's ability to use regular expressions. If the line contains the regular expression, 'Skype$', it will print the first column, then exit
The only problem is that if you had a command Foo Skype, this will also pick it up. To eliminate that, you'll have to do a bit more fancy footwork:
ps -eo pid,comm | while read pid command
do
if [[ "$command" = "Skype" ]]
then
echo $pid
break
fi
done
The while read is reading two variables. The trick is that read uses white space to divide the variables it reads in. However, since there are only two variables, the last one will contain the rest of the entire line. Thus if the command is Skype Controller, the entire command will be put into $command even though there's a space in it.
Now, we don't have to use a regular expression. We can compare the command with an equality.
This is longer to type in, but you're actually using fewer commands and less piping. Remember awk is looping through each line. All you're doing here is making it more explicit. In the end, this is actually much more efficient that what you originally had.
If pgrep is available on Mac, you can use pgrep '^Skype$'. This will list the process id of all processes called Skype.
You used the wrong quotes in your script:
ps -clx | grep "$1" | awk '{print $2}' | head -1
or
pgrep "^$1$"
The problem with your second example is that the $1 is in single quotes, which prevents bash from expanding the variable. There is already a utility that accomplishes what you want without manually parsing ps output.
pgrep "$1"
You can do this in AppleScript:
tell application "System Events"
set skypeProcess to the process "Skype"
set pid to the unix id of skypeProcess
pid
end tell
which means you can use 'osascript' to get the PID from within a shell script:
$ osascript -e "tell application \"System Events\"" -e "set skypeProcess to the process \"Skype\"" -e "set pid to the unix id of skypeProcess" -e "pid" -e "end tell"
3873
You can format the output of ps using the -o [field],... and list by process name using -C [command_name] ;however, ps will still print the column header, which can be removed by piping it through grep -v PID
ps -o pid -C "$1" |grep -v PID
where $1 would be the command name (in this case Skype)
I'd so something like:
ps aux | grep Skype | awk 'NR==1 {print $2}'
==== UPDATE ====
Use the parameter without quotes and use single quotes for awk
#!/bin/bash
ps aux | grep $1 | awk 'NR==1 {print $2}'
Method 1 - Use awk
I don't see any reason to use the -l flag (long format), I also don't see any reason to use grep and awk at the same time: awk has grep capability built in. Here is my plan: use ps and output just 2 columns: pid and command, then use awk to pick out what you want:
ps -cx -o pid,command | awk '$2 == "Skype" { print $1 }'
Method 2 - Use bash
This method has the advantage that if you already script in bash, you don't even need awk, which save one process. The solution is longer than the other method, but very straight forward.
#!/bin/bash
ps -cx -o pid,command | {
while read pid command
do
if [ "_$command" = "_$1" ]
then
# Do something with the pid
echo Found: pid=$pid, command=$command
break
fi
done
}
pgrep myAwesomeAppName
This works great under Catalina 10.15.2
Use double quotes to allow bash to perform variable substitution.
Single quotes disable bash variable substitution mechanism.
ps -clx | grep "$1" | awk "{print $2}" | head -1