I have a command like this :
cat error | grep -o [0-9]
which is printing only numbers like 2,30 and so on. Now I wish to pass this number to sed.
Something like :
cat error | grep -o [0-9] | sed -n '$OutPutFromGrep,$OutPutFromGrepp'
Is it possible to do so?
I'm new to shell scripting. Thanks in advance
If the intention is to print the lines that grep returns, generating a sed script might be the way to go:
grep -E -o '[0-9]+' error | sed 's/$/p/' | sed -f - error
You are probably looking for xargs, particularly the -I option:
themel#eristoteles:~$ xargs -I FOO echo once FOO, twice FOO
hi
once hi, twice hi
there
once there, twice there
Your example:
themel#eristoteles:~$ cat error
error in line 123
error in line 234
errors in line 345 and 346
themel#eristoteles:~$ grep -o '[0-9]*' < error | xargs -I OutPutFromGrep echo sed -n 'OutPutFromGrep,OutPutFromGrepp'
sed -n 123,123p
sed -n 234,234p
sed -n 345,345p
sed -n 346,346p
For real-world use, you'll probably want to pass sed an input file and remove the echo.
(Fixed your UUOC, by the way. )
Yes you can pass output from grep to sed.
Please note that in order to match whole numbers you need to use [0-9]* not only [0-9] which would match only a single digit.
Also note you should use double quotes to get variables expanded(in the sed argument) and it seems you have a typo in the second variable name.
Hope this helps.
Related
I have defined two variables as follows:
var1=$(unzip -c ./*.zip | grep -n "Channel8"| cut -f1 -d":")
var2=$(unzip -c ./*.zip | grep -n "Channel10"| cut -f1 -d":")
I have a very big file and I would like to extract the range of lines between $var1 and $var2 using sed. I am trying the following
sed -n '/"$var1","$var"2p' $(unzip -c ./*.zip)
But with no success. Could you give an explanation why and how to fix it? Thanks.
You can use:
unzip -c ./*.zip | sed -n "$var1,$var2 p"
Fixes are:
Not using single quotes around shell variable
Removal of leading / from sed command
Use of pipeline instead of command substitution
Variables aren't expanded inside single quotes. Also, you need to pipe the output of unzip to sed, not use it as command-line arguments.
unzip -c ./*.zip | sed -n "${var1},${var2}p"
But it seems like you're doing this the hard way, reading the zip file 3 times. Just use the pattern you want to match as the range:
unzip -c ./*.zip | sed -n '/^extracting:.*Channel8/,/^extracting:.*Channel10/p'
Use double quotes to expand the vars:
sed -n "${var1},${var2}p" $(unzip -c ./*.zip)
I have a file with more than 10000 lines. I am trying to search for a string in between particular set of lines, between 2 timestamps.
I am using sed command to achieve this.
sed -n '1,4133p' filename | sed -n '/'2015-08-12'/, /'2015-09-12'/p' filename | grep -i "string"
With the above command I am getting desired result. The above command is considering entire file not the lines I have specified.
Is there is a way to achieve this?.
Please help
I think the problem is here:
sed -n '1,4133p' filename | sed -n '/'2015-08-12'/, /'2015-09-12'/p' filename |
^^^
You want to pipe the output of your first sed command into the second. The way you have this, the output from the first is clobbered and replaced with a re-scan of the file.
Try this:
sed -n '1,4133p' filename | sed -n '/'2015-08-12'/, /'2015-09-12'/p' | grep -i "string"
Any time you find yourself chaining together pipes of seds and greps stop and just use 1 awk command instead:
awk -v IGNORECASE=1 '/2015-08-12/{f=1} f&&/string/; /2015-09-12/||(NR==4133){exit}' file
The above uses GNU awk for IGNORECASE, with other awks you'd just change /string/ to tolower($0)~/string/.
I have been trying to get the head utility to display all but the last line of standard input. The actual code that I needed is something along the lines of cat myfile.txt | head -n $(($(wc -l)-1)). But that didn't work. I'm doing this on Darwin/OS X which doesn't have the nice semantics of head -n -1 that would have gotten me similar output.
None of these variations work either.
cat myfile.txt | head -n $(wc -l | sed -E -e 's/\s//g')
echo "hello" | head -n $(wc -l | sed -E -e 's/\s//g')
I tested out more variations and in particular found this to work:
cat <<EOF | echo $(($(wc -l)-1))
>Hola
>Raul
>Como Esta
>Bueno?
>EOF
3
Here's something simpler that also works.
echo "hello world" | echo $(($(wc -w)+10))
This one understandably gives me an illegal line count error. But it at least tells me that the head program is not consuming the standard input before passing stuff on to the subshell/command substitution, a remote possibility, but one that I wanted to rule out anyway.
echo "hello" | head -n $(cat && echo 1)
What explains the behavior of head and wc and their interaction through subshells here? Thanks for your help.
head -n -1 will give you all except the last line of its input.
head is the wrong tool. If you want to see all but the last line, use:
sed \$d
The reason that
# Sample of incorrect code:
echo "hello" | head -n $(wc -l | sed -E -e 's/\s//g')
fails is that wc consumes all of the input and there is nothing left for head to see. wc inherits its stdin from the subshell in which it is running, which is reading from the output of the echo. Once it consumes the input, it returns and then head tries to read the data...but it is all gone. If you want to read the input twice, the data will have to be saved somewhere.
Using sed:
sed '$d' filename
will delete the last line of the file.
$ seq 1 10 | sed '$d'
1
2
3
4
5
6
7
8
9
For Mac OS X specifically, I found an answer from a comment to this Q&A.
Assuming you are using Homebrew, run brew install coreutils then use the ghead command:
cat myfile.txt | ghead -n -1
Or, equivalently:
ghead -n -1 myfile.txt
Lastly, see brew info coreutils if you'd like to use the commands without the g prefix (e.g., head instead of ghead).
cat myfile.txt | echo $(($(wc -l)-1))
This works. It's overly complicated: you could just write echo $(($(wc -l)-1)) <myfile.txt or echo $(($(wc -l <myfile.txt)-1)). The problem is the way you're using it.
cat myfile.txt | head -n $(wc -l | sed -E -e 's/\s//g')
wc consumes all the input as it's counting the lines. So there is no data left to read in the pipe by the time head is started.
If your input comes from a file, you can redirect both wc and head from that file.
head -n $(($(wc -l <myfile.txt) - 1)) <myfile.txt
If your data may come from a pipe, you need to duplicate it. The usual tool to duplicate a stream is tee, but that isn't enough here, because the two outputs from tee are produced at the same rate, whereas here wc needs to fully consume its output before head can start. So instead, you'll need to use a single tool that can detect the last line, which is a more efficient approach anyway.
Conveniently, sed offers a way of matching the last line. Either printing all lines but the last, or suppressing the last output line, will work:
sed -n '$! p'
sed '$ d'
Here is a one-liner that can get you the desired output, and it can be used more generally for getting all lines from a file except the last n lines.
grep -n "" myfile.txt \ # output the line number for each line
| sort -nr \ # reverse the file by using those line numbers
| sed '1,4d' \ # delete first 4 lines (last 4 of the original file)
| sort -n \ # reverse the reversed file (correct the line order)
| sed 's/^[0-9]*://' # remove the added line numbers
Here is the above command in an actual single line and runnable (can't execute the above due to the added comments):
grep -n "" myfile.txt | sort -nr | sed '1,4d' | sort -n | sed 's/^[0-9]*://'
It's a little cumbersome, and this problem can be solved with more comprehensive commands like ghead, but when you can't or don't want to download such tools, it's nice to be able to do this with the more basic options. I've been in situations where it's simply not an option to get better tools.
awk 'NR>1{print p}{p=$0}'
For this job, an awk one-liner is a bit longer than a sed one.
I've long been wondering about this question;
say I first try to grep some lines from a file:
cat 101127_2.bam |grep 'TGATTACTTGCTTTATTTTAGTGTTTAATTTGTTCTTTTCTAATAA'
Then it'll pop out the whole line containing this string.
However, can we use some simple bash code to locate at which line this string locates? (100th? 1000th?...)
grep -n 'TGATTACTTGCTTTATTTTAGTGTTTAATTTGTTCTTTTCTAATAA' 101127_2.bam
I found it using man grep and writing /line number
// EDIT: Thanks #Keith Thompson I'm editing post from cat file | grep -n pattern to grep -n pattern file, I was in a hurry sorry
try this:
cat 101127_2.bam |grep -n 'TGATTACTTGCTTTATTTTAGTGTTTAATTTGTTCTTTTCTAATAA'
This might work for you too:
sed '/TGATTACTTGCTTTATTTTAGTGTTTAATTTGTTCTTTTCTAATAA/=;d' 101127_2.bam
or
sed -n '/TGATTACTTGCTTTATTTTAGTGTTTAATTTGTTCTTTTCTAATAA/=' 101127_2.bam
The above solutions only output the matching line numbers, to see the lines matched too:
sed '/TGATTACTTGCTTTATTTTAGTGTTTAATTTGTTCTTTTCTAATAA/!d;=' 101127_2.bam
or
sed -n '/TGATTACTTGCTTTATTTTAGTGTTTAATTTGTTCTTTTCTAATAA/{=;p}' 101127_2.bam
Using sed what is an one liner to print the first n characters? I am doing the following:
grep -G 'defn -test.*' OctaneFullTest.clj | sed ....
Don't use sed, use cut:
grep .... | cut -c 1-N
If you MUST use sed:
grep ... | sed -e 's/^\(.\{12\}\).*/\1/'
colrm x
For example, if you need the first 100 characters:
cat file |colrm 101
It's been around for years and is in most linux's and bsd's (freebsd for sure), usually by default. I can't remember ever having to type apt-get install colrm.
don't have to use grep either
an example:
sed -n '/searchwords/{s/^\(.\{12\}\).*/\1/g;p}' file
How about head ?
echo alonglineoftext | head -c 9
To print the N first characters you can remove the N+1 characters up to the end of line:
$ sed 's/.//5g' <<< "defn-test"
defn
Strictly with sed:
grep ... | sed -e 's/^\(.\{N\}\).*$/\1/'