Q. I want to change the formatting of a file. I just wanted to remove all blank lines from text file. How do I achieve this task w/o spending much time?
A. Yes, you do not have to waste your time making manual changes to files. Both Linux and UNIX systems come with file manipulation tools that can be used to remove all blank lines very quickly.
Task: Remove blank lines using sed
Type the following command:
$ sed '/^$/d' input.txt > output.txt
Task: Remove blank lines using grep
$ grep -v '^$' input.txt > output.txt
Both grep and sed use special pattern ^$ that matchs the blank lines. Grep -v option means print all lines except blank line.
Let us say directory /home/me/data/*.txt has all text file. Use following for loop (shell script) to remove all blank lines from all files stored in /home/me/data directory:
#!/bin/sh files="/home/me/data/*.txt" for i in $files do sed '/^$/d' $i > $i.out mv $i.out $i done |
Updated for accuracy.
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31 comment
Is that last shell script wrong? The for loop is using variable f, and inside the loop, everything is using variable i. I think the script should look more like:
#!/bin/sh
files=”/home/me/data/*.txt”
# Next line is changed to use variable i, not f
for i in $files
do
sed ‘/^$/d’ $i > $i.out
mv $i.out $i
done
Hello!
Little fix in this BASH script:
#!/bin/bash
#!/bin/sh
files=”/home/tiger/test_moduls/*.txt”
for i in $files
do
sed ‘/^ *$/d’ $i > $i.out
mv $i.out $i
done
Good Luck! :-)
its nice..appreciable
James,
Thanks for the heads up. The faq has been updated.
When writing to the same file, or a different file and using the redirect > the file ends up blank.
This removes blank lines from input.txt
sed ‘/^$/d’ -i input.txt
Hi,
I tried to use the command sed given above to remove blank line from my file.
The file looks good except one strange behaviour:
“Always” the last line of the file is removed..for example:
test.p is the file and following are the contents of the file:
BEFORE RUNNING THE SED COMMAND:
“this is test 1.
this is test 2.
this is test 3.”
AFTER RUNNING THE SED COMMAND:
“this is test 1.
this is test 2.”
As you can see the last line (“this is test 3.”) is removed after running the command.
If I put the blank line at the end it removes the blank line i.e.
“this is test 1.
this is test 2.
this is test 3.
”
becomes…….
“this is test 1.
this is test 2.
this is test 3.”
Do let me know what I should do in this case?
Waiting for your prompt reply…!
Thanks and Best Regards,
Prashant Deshani
Actually, grep’s -v (–invert-match) option inverts the sense of matching, thus selecting non-matching lines.
Therefore, only when combining it with the pattern ‘^$’ does it mean to select everything except blank lines.
Just thought the way you explained it might be confusing for beginners. When I was new to shell and Linux, most of the guides or forums were useless because they all assumed that the person that needs help has some high understanding of shell or Linux already, and thus they use a lot of terms that person would have never heard of before or they don’t explain anything. Once you have a basic understanding, the learning comes easier, but in the beginning, the learning curve has an almost horizontal slope.
Hi,
I am Siva Saran
I am new to linux environment
can any on tell plz that how to get a particular line from a file using linux commands
For example say that inputfile has lines as follows
total 0
d [RWCEAFMS] MRohit 512 Apr 15 03:15 3.1_SP1_Beta1_127
d [RWCEAFMS] MRohit 512 Apr 14 03:26 3.1_SP1_125 d [RWCEAFMS] MRohit 512 Apr 14 03:26 3.1_SP1_259
d [RWCEAFMS] MRohit 512 Apr 14 03:26 3.0_SP4_IR3_62
Now I want the line which is having SP1_125 ie., line number 3 and store it in an variable
plz can any tell the answer plz
can u mail to {snip_no_email_ids}
what if there’s spaces and tab in the line I want to delete?
thanks,
Renz
This is old, but in case no-one told you:
\w is the special regular expression for whitespace. Both the sed and grep matches should be changed to:
/^\w*$/
-Angwe
Hi,
Using the command
grep -R “SP1_125”
you can get the lines with SP1_125.
if you want to assign to a variable then use
var_a=$(grep -R “SP1_125” )
where is the name of file
var_a = $(grep -R “SP1_125” <filename>)
Hi,
var_a=$(grep -R “SP1_125” filename)
This is quite helpful. Thanks!!
how count all lines in all files in current dir and omit empty lines with wc, grep, cut and bc commands
echo `wc -l * | grep total | cut -f2 -d’ ‘` – `grep -in “^$” * | wc -l ` | bc
@sobi3ch
LOL, wut? Wanna win an obfuscation contest?
would be better, because it doesn’t count lines with only whitespaces, and uses only two instead of seven(!) programs.
for f in *; do awk '!/^\w*$/ && !/^\w*#/ {x++} END {print FILENAME" :"x" lines"}' $f; donewill print you the number of lines, excluding empty lines and lines starting with “#” for every file separately in the current directory.
All you are trying to do is this:
grep -v “^$” * | wc -l
The example should read
and
#!/bin/sh files="/home/me/data/*.txt" for i in $files; do sed -i '/^\w*$/d' $i doneBecause
a) using “^\w*$” instead of “^*$” removes also lines consisting only of whitespaces
b) sed <em-i (=in-place) will edit the files directly, so that there is no need for output redirection and file renaming.
If you have an non-GNU sed version, which doesn’t support in-place editing, than at least change the sed/mv lines to
otherwise you could end up with a lot of empty files, if the sed command goes wrong.
“sed <em-i" should read sed i
“sed <em-i" should read "sed -i“
I would like to know how i can write a shell script to delete “datetime message” and a particular patern exists? in short I want my file to this following output.
### original file ###
datetime message
2011-07-13 13:45:35 Hello World of War Craft
2011-07-13 13:48:43 This is a Test of text
### output file ###
20110713134535 | Hello World of War Craft
20110713134843 | This is a Test of text
thanks
Type
echo '2011-07-13 13:45:35 Hello World of War Craft' | sed -e 's/-//g' -e 's/://g' | awk '{ print $1$2 " | " substr($0, index($0,$3))}'Result:
You need to process the file using while loop:
while IFS= read -r line do echo "$line" | sed -e 's/-//g' -e 's/://g' | awk '{ print $1$2 " | " substr($0, index($0,$3))}' done < "input.txt"There may be a better solution to reduced awk, but I’m too lazy to try it out ;)
Thanks for fast reply,
when I run this shell script
# while IFS= read -r line; do echo “$line” | sed -e ‘s/-//g’ -e ‘s/://g’ | awk ‘{ print $1$2 ” | ” substr($0, index($0,$3))}’; done testdb1.pl;
the file output is below: the line 1 not remove and added datetimemessage, is there any way to remove the line 1 which is “datetimemessage | datetime message”
datetimemessage | datetime message
20110713134535 | Hello World of War Craft
20110713134843 | This is a Test of text
while IFS= read -r line; do echo “$line” | sed -e ‘s/-//g’ -e ‘s/://g’ | awk ‘{ print $1$2 ” | ” substr($0, index($0,$3))}’; done testdb1.pl;
correction
‘; done testdb.pl “>testdb.pl”
Hi all,
I don’t if is the right to post this issue,
is there any way to dump the new insert data to a textfile with shell script, for ie. after insertion to the mysql database execute the shell script to append and append the new record?
thanks
Hi all,
Is there a way to add an empty line for every 5 lines of data using grep?
line1
line2
line3
line4
line5
(empty line)
line6
line7
line8
line9
line10
(empty line)
you can also do cat output.txt | awk ‘NF’ >> output.txt
grep -v “^[[:blank:]]*$”
i have a text file that in end of file have a blank line but i cant delet in by sed i have to vi it and use dd command to delet it
I am using the command :-
I get the output like this,
Database Size Used space Free space 22 GB 17 GB 5 GB in the output of text file.
I want the output like this in the text file.
Please let me know which command need to use?