Hi have the following command:
lsscsi | grep HITACHI | awk '{print $6}'
I want that the output will be the number of lines of the original output.
For example, if the original output is:
/dev/sda
/dev/sdb
/dev/sdc
The final output will be 3.
Basically the command wc -l can be used to count the lines in a file or pipe. However, since you want to count the number of lines after a filter has been applied I would recommend to use grep for that:
lsscsi | grep -c 'HITACHI'
-c just prints the number of matching lines.
Another thing. In your example you are using grep .. | awk. That's a useless use of grep. It should be
lsscsi | awk '/HITACHI/{print $6}'
Related
$ lsusb --verbose | grep "THRSL_C_C_V"
results in:
iManufacturer 1 THRSL_C_C_V3.07
I want to extract the word THRSL_C_C_V3.07 only.
I tried lsusb --verbose | grep -w "THRSL_C_C_V". Didn't show anything.
Try:
lsusb --verbose | grep -o "THRSL_C_C_V3\.07"
The -o options results in only matching text, the backlash escapes the dot allowing an exact match of the requested text.
You may use awk instead of grep:
lsusb --verbose | awk '/THRSL_C_C_V/{print $3}'
This awk command searches a line that has text THRSL_C_C_V in it and by using print $3 we make sure to print 3rd column of matched line.
Alternatively you can use grep -o like this:
echo 'iManufacturer 1 THRSL_C_C_V3.07' |
grep -oE 'THRSL_C_C_V[^[:blank:]]*'
THRSL_C_C_V3.07
Use the following:-
$ lsusb --verbose | grep "THRSL_C_C_V" | awk '{print $NF}'
or
$ lsusb --verbose | awk '/THRSL_C_C_V/{print $NF}'
Here, $NF will be used for the last element of output
Currently I'm trying to tail a log but only showing the lines that has some keywords. Currently I'm using
tail -F file.log | grep -ie 'error\|fatal\|exception\|shutdown\|started'
and I'm getting the expected results: (for example)
10:22 This is an error
10:23 RuntimeException: uncaught problem
I also want to exclude lines that contain a <DATATAG>, even if the keywords slipped into it, because it contains a lot of binary data that clutters my log. I'm then trying to add to the pipe another grep that excludes the tag:
tail -F file.log | grep -ie 'error\|fatal\|exception\|shutdown\|started' | grep -vF '<DATATAG>'
However, this time no lines appear, not even the previous ones that has 'error'/'exception' but not <DATATAG>. When I tried the excluding grep alone:
tail -F file.log | grep -vF '<DATATAG>'
all lines appear, including those that have 'error'/'exception'.
Am I doing something wrong?
Your problem is one of buffering. grep is a tricky tool when it comes to that. From the man page:
By default, output is line buffered when standard output is a terminal and block buffered otherwise.
In your example, the first grep is buffering at the block level, so it will not turn an output to the 2nd grep for a while. The solution is to use the --line-buffered option to look like:
tail -F file.log | grep --line-buffered -ie 'error\|fatal\|exception\|shutdown\|started' | grep -vF '<DATATAG>'
Consider:
var=`ls -l | grep TestFile.txt | awk '{print $5}'`
I am able to read file size, but how does it work?
Don't parse ls
size=$( stat -c '%s' TestFile.txt )
Yes, so basically you could divide it into 4 parts:
ls -l
List the current directory content (-l for long listing format)
| grep TestFile.txt
Pipe the result and look for the file you are interested in
| awk '{print $5}
Pipe the result to awk program which cuts (by using spaces as separator) the fifth column which happens to be the file size in this case (but this can be broken by spaces in the filename, for example)
var=`...`
The backquotes (`) enclose commands. The output of the commands gets stored in the var variable.
NOTE: You can get the file size directly by using du -b TestFile.txt or stat -c %s TestFile.txt
I'm connecting to an exadata and want to get information about "ORACLE_HOME" variable inside them. So i'm using this command:
ls -l /proc/<pid>/cwd
this is the output:
2 oracle oinstall 0 Jan 23 21:20 /proc/<pid>/cwd -> /u01/app/database/11.2.0/dbs/
i need the get the last part :
/u01/app/database/11.2.0 (i dont want the "/dbs/" there)
i will be using this command several times in different machines. So how can i get this substring from whole output?
Awk and grep are good for these types of issues.
New:
ls -l /proc/<pid>/cwd | awk '{print ($NF) }' | sed 's#/dbs/##'
Old:
ls -l /proc/<pid>/cwd | awk '{print ($NF) }' | egrep -o '^.+[.0-9]'
Awk prints the last column of the input which is your ls command and then grep grabs the beginning of that string up the last occurrence of numbers and dots. This is a situational solution and perhaps not the best.
Parsing the output of ls is generally considered sub-optimal. I would use something more like this instead:
dirname $(readlink -f /proc/<pid>/cwd)
What is the construct in bash called where you can take wrap a command that outputs to stdout, such that the output itself is treated like a stream? In case I'm not describing that so well, maybe an example will do best, and this is what I typically use it for: applying diff to output that does not come from a file, but from other commands, where
cmd
is wrapped as
<(cmd)
By wrapping a command in such a manner, in the example below I determine that there a difference of one between the two commands that I am running, and then I am able to determine that one precise difference. What is the construct/technique of wrapping a command as <(cmd) called? Thanks
[builder#george v6.5 html]$ git status | egrep modified | awk '{print $3}' | wc -l
51
[builder#george v6.5 html]$ git status | egrep modified | awk '{print $3}' | xargs grep -l 'Ext\.define' | wc -l
50
[builder#george v6.5 html]$ diff <(git status | egrep modified | awk '{print $3}') <(git status | egrep modified | awk '{print $3}' | xargs grep -l 'Ext\.define')
39d38
< javascript/reports/report_initiator.js
ADDENDUM
The revised command using the advice for using git's ls-file should be as follows (untested):
diff <(git ls-files -m) <(git ls-files -m | xargs grep -l 'Ext\.define')
It is called process substitution.
This is called Process Substitution
This is process substitution, as you have been told. I'd just like to point out that this also works in the other direction. Process substitution with >(cmd) allows you to take a command that writes to a file and instead have that output redirected to another command's stdin. It's very useful for inserting something into a pipeline that takes an output filename as an argument. You don't see it as much because pretty much every standard command will write to stdout already, but I have used it often with custom stuff. Here is a contrived example:
$ echo "hello world" | tee >(wc)
hello world
1 2 12