I want to make a simple dmenu command that reads a file of commands and names. Then takes the names and displays them using dmenu then takes dmenu's output and runs the associated command using the file again.
I got to the point where dmenu displays the names, but I don't really know where to go from there. Learning bash is a really daunting task to me and I don't really know where to start with this seemingly simple script/command.
here is the file:
Pushbullet
google-chrome-stable --app=https://www.pushbullet.com
Steam
steam
Chrome
google-chrome-stable
Libre Office
libreoffice
Transmission
transmission-qt
Audio Control Panel
sudo pavucontrol & bluberry
and here is what I have so far for my command:
awk 'NR % 2 != 0' /home/rocco/programlist | dmenu | ??(grep -l "stdout" /home/rocco/programlist....)
It was my thinking that I could somehow pipe into grep or awk with the name of the application then get the line number then add one and pipe that into sh.
Thanks
I have no experience with dmenu but if I understand how it works correctly, this should do what you want. Wrapping a command in $(…) returns the output as a variable, which we can pass on to another command.
#!/bin/bash
plist="/home/rocco/programlist"
# pipe every second line to dmenu
selected=$(awk 'NR % 2 != 0' "$plist" | dmenu)
# search for the selected item, get the command after it
cmd=$(grep -A1 "$selected" "$plist" | tail -n 1)
# run the command
$cmd
Worth mentioning a mistake in your question. dmenu sends to stdout, or standard output, but the next program in line would be reading stdin, or standard input. In any case, grep can't take patterns on standard input, which is why I've saved to a variable instead of trying to pipe it somewhere.
Assuming you have programlist.txt in the working directory you can use:
awk 'NR%2 !=0' programlist.txt |dmenu |awk '{system("grep --no-group-separator -A 1 '"'"'"$0"'"'"' programlist.txt");}' |awk '{if(NR==2){system($0);}}'
Note the quoting of the $0 in the first awk envocation. This is necessary to get names with spaces in them like "Libre Office"
Related
I've read here that
To make a pipe, put a vertical bar (|) on the command line between two commands.
then
When a program takes its input from another program, performs some operation on that input, and writes the result to the standard output, it is referred to as a filter.
So I've first tried the ls command whose output is:
Desktop HelloWord.java Templates glassfish-4.0
Documents Music Videos hs_err_pid26742.log
Downloads NetBeansProjects apache-tomcat-8.0.3 mozilla.pdf
HelloWord Pictures examples.desktop netbeans-8.0
Then ls | echo which outputs absolutely nothing.
I'm looking for a way to take advantages of pipelines and filters in my bash script. Please help.
echo doesn't read from standard input. It only writes its command-line arguments to standard output. The cat command is what you want, which takes what it reads from standard input to standard output.
ls | cat
(Note that the pipeline above is a little pointless, but does demonstrate the idea of a pipe. The command on the right-hand side must read from standard input.)
Don't confuse command-line arguments with standard input.
echo doesn't read standard input. To try something more useful, try
ls | sort -r
to get the output sorted in reverse,
or
ls | grep '[0-9]'
to only keep the lines containing digits.
In addition to what others have said - if your command (echo in this example) does not read from standard input you can use xargs to "feed" this command from standard input, so
ls | echo
doesn't work, but
ls | xargs echo
works fine.
I am currently trying to make a script file that runs multiple other script files on a server. I would like to display the output of these script to the screen IN ADDITION to passing it into grep so I can do error testing. currently I have written this:
status=$(SOMEPROCESS | grep -i "SOMEPROCESS started completed correctly")
I do further error handling below this using the variable status, so I would like to display SOMEPROCESS's output to the screen for error reference. This is a read only server and I can not save the output to a log file.
You need to use the tee command. It will be slightly fiddly, since tee outputs to a file handle. However you could create a file descriptor using pipe.
Or (simpler) for your use case.
Start the script without grep and pipe it through tee SOMEPROCESS | tee /my/safely/generated/filename. Then use tail -f /my/safely/generated/filename | grep -i "my grep pattern separately.
You can use process substituion together with tee:
SOMEPROCESS | tee >(grep ...)
This will use an anonymous pipe and pass /dev/fd/... as file name to tee (or a named pipe on platforms that don't support /dev/fd/...).
Because SOMEPROCESS is likely to buffer its output when not talking to a terminal, you might see significant lag in screen output.
I'm not sure whether I understood your question exactly.
I think you want to get the output of SOMEPROCESS, test it, print it out when there are errors. If it is, I think the code bellow may help you:
s=$(SOMEPROCESS)
grep -q 'SOMEPROCESS started completed correctly' <<< $s
if [[ $? -ne 0 ]];then
# specified string not found in the output, it means SOMEPROCESS started failed
echo $s
fi
But in this code, it will store the all output in the memory, if the output is big enough, there will be a OOM risk.
I use screen to run a minecraft server .jar, and I would like to write a bash script to see if the most recent line has changed every five minutes or so. If it has, then the script would start from the beginning and make the check again in another five minutes. If not, it should kill the java process.
How would I go about getting the last line of text from a screen via a bash script?
If I have understand, you can redirect the output of your program in a file and work on it, with the operator >.
Try to run :
ls -l > myoutput.txt
and open the file created.
You want to use the tail command. tail -n 1 will give you the last line of the file or redirected standard output, while tail -f will keep the tail program going until you cancel it yourself.
For example:
echo -e "Jello\nPudding\nSkittles" | tail -n 1 | if grep -q Skittles ; then echo yes; fi
The first section simply prints three lines of text:
Jello
Pudding
Skittles
The tail -n 1 finds the last line of text ("Skittles") and passes that to the next section.
grep -q simply returns TRUE if your pattern was found or FALSE if not, without actually dumping or outputting anything to screen.
So the if grep -q Skittles section will check the result of that grep -q Skittles pattern and, if it found Skittles, prints 'yes' to the screen. If not, nothing gets printed (try replacing Skittles with Pudding, and even though it was in the original input, it never made it out the other end of the tail -n 1 call).
Maybe you can use that logic and output your .jar to standard output, then search that output every 5 minutes?
When I run this command:
ps aux|awk {'print $1,$2,$3,$11'}
I get a listing of the user, PID, CPU% and the actual command.
I want to pipe all those listings into a shell script to calculate the CPU% and if greater than, say 5, then to kill the process via the PID.
I tried piping it to a simple shell script, i.e.
ps aux|awk {'print $1,$2,$3,$11'} | ./myscript
where the content of my script is:
#!/bin/bash
# testing using positional parameters
echo "$1 $2 $3 $4"
But I get a blank output. Any idea how to do this?
Many thanks!
If you use awk, you don't need an additional bash script. Also, it is a good idea to reduce the output of the ps command so you don't have to deal with extra information:
ps acxho user,pid,%cpu,cmd | awk '$3 > 5 {system("echo kill " $2)}'
Explanation
The extra ps flags I use:
c: command only, no extra arguments
h: no header, good for scripting
o: output format. In this case, only output the user, PID, %CPU, and command
The awk command compare the %CPU, which is the third column, with a threshold (5). If it is over the threshold, then issue the system command to kill that process.
Note the echo in the command. Once you are certain the scripts works the way you like, then remove the word echo from the command to execute it for real.
Your script needs to read its input
#!/bin/bash
while read a b c d; do
echo $a $b
done
I think you can get it using xargs command to pass the AWK output to your script as arguments:
ps aux|awk {'print $1,$2,$3,$11'} | xargs ./myscript
Some extra info about xargs: http://en.wikipedia.org/wiki/Xargs
When piping input from one process to another in Linux (or POSIX-compliant systems) the output is not given as arguments to the receiving process. Instead, the standard output of the first process is piped into the standard input of the other process.
Because of this, your script cannot work. $1...$n accesses variables that have been passed as arguments to it. As there are none it won't display anything. Instead, you have to read the standard input into variables with the read command (as pointed out by William).
The pipe '|' redirects the standard output of the left to the standard input of the right. In this case, the output of the ps goes to the input of awk, then the output of awk goes to the stdin of the script.
Therefore your scripts needs to read its STDIN.
#!/bin/bash
read var1 var2 var3 ...
Then you can do whatever you want with those variables.
More info, type in bash: help read
If I well understood your problem, you want to kill every process that exceeds X% of the CPU (using ps aux).
Here is the solution using AWK:
ps aux | grep -v "%CPU" | awk '{if ($3 > XXX) { print "Killing process with PID "$2", called "$4", consuming "$3"% and launched by "$1; system( "kill -9 " $2 );}}' -
Where XXX is your threshold (% of CPU).
It also prints related info to the killed process, if it is not desired just remove the print statement.
You can add some filters like: do not remove root's process...
Try putting myscript in front like this:
./myscript `ps aux|awk {'print $1,$2,$3,$11'}`
Normally when one wants to look at specific output lines from running something, one can do something like:
./a.out | grep IHaveThisString
but what if IHaveThisString is something which changes every time so you need to first run it, watch the output to catch what IHaveThisString is on that particular run, and then grep it out? I can just dump to file and later grep but is it possible to do something like background it and then bring it to foreground and bringing it back but now piped to some grep? Something akin to:
./a.out
Ctrl-Z
fg | grep NowIKnowThisString
just wondering..
No, it is only in your screen buffer if you didn't save it in some other way.
Short form: You can do this, but you need to know that you need to do it ahead-of-time; it's not something that can be put into place interactively after-the-fact.
Write your script to determine what the string is. We'd need a more detailed example of the output format to give a better example of usage, but here's one for the trivial case where the entire first line is the filter target:
run_my_command | { read string_to_filter_for; fgrep -e "$string_to_filter_for" }
Replace the read string_to_filter_for with as many commands as necessary to read enough input to determine what the target string is; this could be a loop if necessary.
For instance, let's say that the output contains the following:
Session id: foobar
and thereafter, you want to grep for lines containing foobar.
...then you can pipe through the following script:
re='Session id: (.*)'
while read; do
if [[ $REPLY =~ $re ]] ; then
target=${BASH_REMATCH[1]}
break
else
# if you want to print the preamble; leave this out otherwise
printf '%s\n' "$REPLY"
fi
done
[[ $target ]] && grep -F -e "$target"
If you want to manually specify the filter target, this can be done by having the loop check for a file being created with filter contents, and using that when starting up grep afterwards.
That is a little bit strange what you need, but you can do it tis way:
you must go into script session first;
then you use shell how usually;
then you start and interrupt you program;
then run grep over typescript file.
Example:
$ script
$ ./a.out
Ctrl-Z
$ fg
$ grep NowIKnowThisString typescript
You could use a stream editor such as sed instead of grep. Here's an example of what I mean:
$ cat list
Name to look for: Mike
Dora 1
John 2
Mike 3
Helen 4
Here we find the name to look for in the fist line and want to grep for it. Now piping the command to sed:
$ cat list | sed -ne '1{s/Name to look for: //;h}' \
> -e ':r;n;G;/^.*\(.\+\).*\n\1$/P;s/\n.*//;br'
Mike 3
Note: sed itself can take file as a parameter, but you're not working with text files, so that's how you'd use it.
Of course, you'd need to modify the command for your case.