I am trying to count the all processes opened by all commands which contain the word valyria. I thought about this solution:
writing a one-liner, such as number=$(history | grep "valyria" | wc -l) && echo $number, but this does not seem to print anything(the variable has been previously declared).
My other question is this: if I enter a command which contains the word valyrian, will that command open only 1 proceess or more? If the later is true, I guess that my one-liner becomes useless, since it counts 1 match=1 process. How could I achieve the desired result?
Thanks, Polb
Related
im trying to improve my bash on my road to become a DevOps,
one of my excercises states that i should be able to
1-Write a bash script using Vim editor that checks all the processes running for the current user
2-Extend the previous script to ask for a user input for sorting the processes output either by memory or CPU consumption, and print the sorted list.
3-Extend the previous script to ask additionally for user input about how many processes to print. Hint: use head program to limit the number of outputs.
The error message is a syntax error, it doesnt seem to work, any ideas or tips ?
#!/bin/bash
read -p "Press 1- to sort by memory OR 2 to sort by CPU consumption" sorting
read -p "how much output should be displayed, choose a number between 1-9 ?" output
if[$sorting = 1];
ps auck-%mem | head -n $output | grep kami
else
ps auck-%cpu | head -n $output | grep kami
fi
Cheers
Kami
This question already has answers here:
Count number of lines after wrapped by terminal’s length [closed]
(3 answers)
Closed 5 years ago.
If I want to clear the screen and run less if the output of a program exceeds the number of lines on a screen, I can do something like:
mypgm | tee mypgm.out
LEN=$(wc -l mypgm.out | cut -f1 -d' ')
[[ $LEN >= $LINES ]]; then
clear
less -R mypgm.out
fi
It works just fine as long as none of the lines in the output wrap around, visually taking up more than a single line on the screen.
Is there an simple way to determine how many lines of the screen the output occupies visually, or do I have to loop over the output file, computing the number of "lines" a long line needs to display by using $COLUMNS
Seems like you're actually looking for something like:
mycmd | less -F
From man less:
-F or --quit-if-one-screen
Causes less to automatically exit if the entire file can be displayed on the first screen.
You can make it a default behavior with:
export LESS='-F'
in your .bashrc.
The -F option is nicely combined with -X which will skip clearing of the screen before listing (can also have it as a default with LESS='-FX').
I found fold, which solves the problem:
fold -w "$COLUMNS" mypgm.out | wc -l
(no need for the 'cut' since wc is running against a pipe)
I'm trying to find a solution to a problem analog to this one:
#command_A
A_output_Line_1
A_output_Line_2
A_output_Line_3
#command_B
B_output_Line_1
B_output_Line_2
Now I need to compare A_output_Line_2 and B_output_Line_1 and echo "Correct" if they are equal and "Not Correct" otherwise.
I guess the easiest way to do this is to copy a line of output in some variable and then after executing the two commands, simply compare the variables and echo something.
This I need to implement in a bash script and any information on how to get certain line of output stored in a variable would help me put the pieces together.
Also, it would be cool if anyone can tell me not only how to copy/store a line, but probably just a word or sequence like : line 1, bytes 4-12, stored like string in a variable.
I am not a complete beginner but also not anywhere near advanced linux bash user. Thanks to any help in advance and sorry for bad english!
An easier way might be to use diff, no?
Something like:
command_A > command_A.output
command_B > command_B.output
diff command_A.output command_B.output
This will work for comparing multiple strings.
But, since you want to know about single lines (and words in the lines) here are some pointers:
# first line of output of command_A
command_A | head -n 1
The -n 1 option says only to use the first line (default is 10 I think)
# second line of output of command_A
command_A | head -n 2 | tail -n 1
that will take the first two lines of the output of command_A and then the last of those two lines. Happy times :)
You can now store this information in a variable:
export output_A=`command_A | head -n 2 | tail -n 1`
export output_B=`command_B | head -n 1`
And then compare it:
if [ "$output_A" == "$output_B" ]; then echo 'Correct'; else echo 'Not Correct'; fi
To just get parts of a string, try looking into cut or (for more powerful stuff) sed and awk.
Also, just learing a good general purpose scripting language like python or ruby (even perl) can go a long way with this kind of problem.
Use the IFS (internal field separator) to separate on newlines and store the outputs in an array.
#!/bin/bash
IFS='
'
array_a=( $(./a.sh) )
array_b=( $(./b.sh) )
if [ "${array_a[1]}" = "${array_b[0]}" ]; then
echo "CORRECT"
else
echo "INCORRECT"
fi
Normally when one wants to look at specific output lines from running something, one can do something like:
./a.out | grep IHaveThisString
but what if IHaveThisString is something which changes every time so you need to first run it, watch the output to catch what IHaveThisString is on that particular run, and then grep it out? I can just dump to file and later grep but is it possible to do something like background it and then bring it to foreground and bringing it back but now piped to some grep? Something akin to:
./a.out
Ctrl-Z
fg | grep NowIKnowThisString
just wondering..
No, it is only in your screen buffer if you didn't save it in some other way.
Short form: You can do this, but you need to know that you need to do it ahead-of-time; it's not something that can be put into place interactively after-the-fact.
Write your script to determine what the string is. We'd need a more detailed example of the output format to give a better example of usage, but here's one for the trivial case where the entire first line is the filter target:
run_my_command | { read string_to_filter_for; fgrep -e "$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.
I've got a strangely acting egrep -f.
Example:
$ egrep -f ~/tmp/tmpgrep2 orig_20_L_A_20090228.txt | wc -l
3
$ for lines in `cat ~/tmp/tmpgrep2` ; do egrep $lines orig_20_L_A_20090228.txt ; done | wc -l
12
Could someone give me a hint what could be the problem?
No, the files did not changed between executions. The expected answer for the egrep line count is 12.
UPDATE on file contents: the searched file contains cca 13000 lines, each of them are 500 char long, the pattern file contains 12 lines, each of them are 24 char long. The pattern always (and only) occurs on a fixed position in the seached file (26-49).
UPDATE on pattern contents: every pattern from tmpgrep2 are a 24 char long number.
If the search patterns are found on the same lines, then you can get the result you see:
Suppose you look for:
abc
def
ghi
jkl
and the data file is:
abcdefghijklmnoprstuvwxzy
then the one-time command will print 1 and the loop will print 4.
Could it be that the lines read contain something that the shell is expanding/substituting for you, in the second version? Then that doesn't get done by grep when it reads the patterns itself, thus leading to a different sent of patterns being matched.
I'm not totally sure if the shell is doing any expansion on the variable value in an invocation like that, but it's an idea at least.
EDIT: Nope, it doesn't seem to do any substitutions. But it could be quoting issue, if your patterns contain whitespace the for loop will step through each token, not through each line. Take a look at the read bash builtin.
Do you have any duplicates in ~/tmp/tmpgrep2? Egrep will only use the dupes one time, but your loop will use each occurrence.
Get rid of dupes by doing something like this:
$ for lines in `sort < ~/tmp/tmpgrep2 | uniq` ; do egrep $lines orig_20_L_A_20090228.txt ; done | wc -l
I second #unwind.
Why don't you run without wc -l and see what each search is finding?
And maybe:
for lines in `cat ~/tmp/tmpgrep2` ; do echo $lines ; done
Just to see now the shell is handling $lines?
The others have already come up with most of the things I would look at. The next thing I would check is the environment variable GREP_OPTIONS, or whatever it is called on your machine. I've gotten the strangest error messages or behaviors when using a command line argument that interfered with the environment settings.