in place editing using awk - linux

I want to add a line at top of file say f1 using awk.
Is there a better way than the following?
awk 'BEGIN{print "word"};{print $0}' f1 > aux;cp aux f1;\rm aux<br/>
Does awk has something like -i option in sed?


Why not use sed - it would make the solution more straightforward
$sed -i.bak '1i\
word
' <filename>


An alternate way to do this is:
sed -i '1s:^: Word1\nWord2 :' file

Related

How do you change column names to lowercase with linux and store the file as it is?

I am trying to change the column names to lowercase in a csv file. I found the code to do that online but I dont know how to replace the old column names(uppercase) with new column names(lowercase) in the original file. I did something like this:
$cat head -n1 xxx.csv | tr "[A-Z]" "[a-z]"
But it simply just prints out the column names in lowercase, which is not enough for me.
I tried to add sed -i but it did not do any good. Thanks!!

Using awk (readability winner) :
concise way:
awk 'NR==1{print tolower($0);next}1' file.csv
or using ternary operator:
awk '{print (NR==1) ? tolower($0): $0}' file.csv
or using if/else statements:
awk '{if (NR==1) {print tolower($0)} else {print $0}}' file.csv
To change the file for real:
awk 'NR==1{print tolower($0);next}1' file.csv | tee /tmp/temp
mv /tmp/temp file.csv
For your information, sed using the in place edit switch -i do the same: it use a temporary file under the hood.
You can check this by using :
strace -f -s 800 sed -i'' '...' file

Using perl:
perl -i -pe '$_=lc() if $.==1' file.csv
It replace the file on the fly with -i switch

You can use sed to tell it to replace the first line with all lower-case and then print the rest as-is:
sed '1s/.*/\L&/' ./xxx.csv
Redirect the output or use -i to do an in-place edit.
Proof of Concept
$ echo -e "COL1,COL2,COL3\nFoO,bAr,baZ" | sed '1s/.*/\L&/'
col1,col2,col3
FoO,bAr,baZ

sed command inserting text - bash

I am exploring sed function
what I have here is a simple text file shown below
Id,fruit name and quantity. now I want to add the amount of the fruit behind the quantity of each fruit respectively
fruit.txt
1,apple
2,banana
how to make it become like this.
expected output
first input of sed command
my textfile(fruit.txt) will become like this
1,apple,50
2,banana,40

Use sed like this:
sed -i -r 's/(apple)(,[0-9]*)?$/\1,10/'
sed -i -r 's/(apple)(,[0-9]*)?$/\1,20/'
sed -i -r 's/(apple)(,[0-9]*)?$/\1,30/'

use awk:
awk -F, -v OFS="," '/apple/{$3="whatever"}7' file
but if you don't have gnu awk 4.1, you have to do this to write back to the file:
awk -F, -v OFS="," '/apple/{$3="whatever"}7' file >~/foo.tmp && mv ~/foo.tmp file

awk to print some parameters of a line

I have lines in a file in linux, and i am trying print the line without the | and without some parameters
$cat file
2013-07-15,Provider 1.99,3|30000055|2347|0,12222,1,3,0,0,0,19,aaa,bbb
2013-07-15,Provider 1.99,3|30000055|2347|0,12222,44,12,0,0,0,33,aaa,bbb
and i need the output like:
2013-07-15,Provider,2347,12222,1,3,0,0,0,19,aaa,bbb
2013-07-15,Provider,2347,12222,44,12,0,0,0,33,aaa,bbb
and i am trying with awk, but i have some problems.

If your lines have similar pattern you would to retain then you can do:
awk 'BEGIN{FS=OFS=","}{$2="Provider";$3=2347}1' file
If you don't know what the patterns are then here is a more generic one:
awk 'BEGIN{FS=OFS=","}{split($2,a,/ /);split($3,b,/\|/);$2=a[1];$3=b[3]}1' file
If it doesn't solve your problem, I am pretty sure it would help you guide to get one.

Using sed:
sed 's/ [^|]*|[^|]*|\([^|]*\)|[^,]/,\1/' input
and some shorter version:
sed 's/ .*|\([^|]*\)|[^,]*/,\1/' input
and even shorter:
sed 's/ .*|\(.*\)|[^,]*/,\1/' input

Use awk, and let blank or comma or pipe be the field separators:
awk -F '[[:blank:],|]' -v OFS=, '{
print $1,$2,$6,$8,$9,$10,$11,$12,$13,$14,$15,$16
}' file
2013-07-15,Provider,2347,12222,1,3,0,0,0,19,aaa,bbb
2013-07-15,Provider,2347,12222,44,12,0,0,0,33,aaa,bbb

sed extract text between two patterns where second pattern may be either of one

I am trying to extract text between pattern1 (fixed) and pattern2 (this can be p2-1/p2-2).
can you please tell me how to achieve this in a single command?
A file starts with start and ends with either end or close
File1:
======
junktest
data
start
stackoverflow
sed
close
File2:
======
data2
start
stackoverflow
end
I can extract text from File1 with
sed -n "/start/,/close/p"
And from File2 with
sed -n "/start/,/end/p"
I need a single sed command to achieve both..
something like:
sed -n "/start/, /close or end /p"

Both GNU sed and BSD sed:
sed -nE '/start/,/close|end/p' file

This awk looks better
awk '/start/,/end|close/' file

sed -n -E "/Word1/,/Word2-1/p" | sed -n -E "/Word1/,/Word2-2/p"

Easy with awk:
$ awk '/start/{p=1}p{print}/end|close/{p=0}' file

How to delete lines from file with sed\awk?

I have file, with lines, contains ip with netmask
a.b.c.d/24
w.x.y.z/32
etc
How to delete delete specific row?
i'm using
sed -ie "s#a.b.c.d/24##g" %filname%
but after the removal is an empty string in file.
It should run inside a script, with ip as parameter and also work in freebsd under sh.

Sed solution
sed -i '/<pattern-to-match-with-proper-escape>/d' data.txt
-i option will change the original file.
Awk solution
awk '!/<pattern-to-match-with-proper-escape>/' data.txt

Using sed:
sed -i '\|a.b.c.d/24|d' file
Command line arg:
For the input being command line argument, say 1st argument($1):
sed -i "\|$1|d" file
Replace $1 with appropriate argument number as is your case.

You should use d (delete) not g. Also do not use s (replacement).
sed -ie '/a.b.c.d\/24/d' %filename%
In a script you should using it in this way
IP=$1
IPA=${IP////\\/}
sed -i /"${IPA}"/d %filename%
And the script parameter should be called in this way:
./script.sh a.b.c.d/24

perl -i -lne 'print unless(/a.b.c.d\/24/)' your_file
or in awk if you donot want to do inplace editing:
awk '$0!~/a.b.c.d\/24/' your_file

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