How to get process id from process name? - macos

Question

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?

Answer 1

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.

Answer 2

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 "^$1$"

Answer 3

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"

Answer 4

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

Answer 5

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)

Answer 6

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}'

Answer 7

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
}

Answer 8

pgrep myAwesomeAppName
This works great under Catalina 10.15.2

Answer 9

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