Using AWK in a for loop


 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Using AWK in a for loop
# 1  
Old 08-25-2009
Using AWK in a for loop

Hello,

I am trying to use AWK to print only the first field of numerous text files, and then overwrite these files. They are of the format 1*2,3,4,5. I have tried the following code (using tcsh):

Code:
 foreach f (file1 file2 file3)
cat $f | awk -F'*' '{print $1}' > $f
end

However, I get very inconsistent results each time I run this script. I have tried creating a tmp directory where I run the above command on a clean set of the files. But, sometimes it returns empty files, whereas other times it runs fine for all the files. Any ideas on what is going on here, or if there is a better way to get awk to do what I want?

On a side note, I have tried a similar method using cut:

Code:
 foreach f (file1 file2 file3)
cat $f | cut -d'*' -f1 > $f
end

but I get the same inconsistencies.


Thank you for your help,

-Jahn
# 2  
Old 08-25-2009
The below line should be re-written..
Code:
cat $f | awk -F'*' '{print $1}' > $f

Try:
Code:
awk -F'*' '{print $1}' $f > _temp
mv ${_temp} $f

# 3  
Old 08-25-2009
I'd personally get rid of the brackets around the foreach, but i dont know tcsh so it may be a requirement. It should work doing
Code:
 for file in file1 file2 file3 ; do awk -F'*' '{print $1}' < $file > $file ; done

???
Quote:
Originally Posted by Jahn
Hello,

I am trying to use AWK to print only the first field of numerous text files, and then overwrite these files. They are of the format 1*2,3,4,5. I have tried the following code (using tcsh):

Code:
 foreach f (file1 file2 file3)
cat $f | awk -F'*' '{print $1}' > $f
end

However, I get very inconsistent results each time I run this script. I have tried creating a tmp directory where I run the above command on a clean set of the files. But, sometimes it returns empty files, whereas other times it runs fine for all the files. Any ideas on what is going on here, or if there is a better way to get awk to do what I want?

On a side note, I have tried a similar method using cut:

Code:
 foreach f (file1 file2 file3)
cat $f | cut -d'*' -f1 > $f
end

but I get the same inconsistencies.


Thank you for your help,

-Jahn
# 4  
Old 08-25-2009
Here is what worked for me:
Code:
 foreach f (*)
awk -F'*' '{print $1}' $f > {$f}_temp
mv {$f}_temp $f
end

I have tried using the "awk code < file > newfile" redirection before, but I always end up with an empty newfile.


Thanks again for your help, guys!
# 5  
Old 09-17-2009
sed 's/\*.*//' deletes everything from first * on lines Smilie
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. UNIX for Beginners Questions & Answers

awk !seen[$]++ in else loop

Hi all, I was searching the net for a solution for my problem... unfortunately nothing so far. I want to sort on more than on column tab delimited file and keep the line if in the column I sort there is no value, but for those who have a value I want them only unique. I have tried the... (5 Replies)
Discussion started by: ksenia
5 Replies

2. UNIX for Beginners Questions & Answers

awk with For loop

Hi My Requirement is to take the sum of each column below is the input file. 1 2 3 4 1 2 3 4 1 2 3 4 Initial i was using below command to achieve my desired result. however this was adding the row and not column. i am not able understand why this is happening awk... (1 Reply)
Discussion started by: scriptor
1 Replies

3. Shell Programming and Scripting

Using awk within a for loop

Hello, I currently have managed to get an awk function working inside a for loop that allows me to combine two files based on their headings but what I have not been able to do is print the output to files with variable names. awk ' NR==FNR {a=$0; next} /^>/ {$0 = $0" "a;} ... (2 Replies)
Discussion started by: Allie_gastrator
2 Replies

4. Shell Programming and Scripting

awk programming -Passing variable to awk for loop

Hi All, I am new to AWK programming. I have the following for loop in my awk program. cat printhtml.awk: BEGIN -------- <some code here> END{ ----------<some code here> for(N=0; N<H; N++) { for(M=5; M<D; M++) print "\t" D ""; } ----- } ... (2 Replies)
Discussion started by: ctrld
2 Replies

5. Shell Programming and Scripting

awk loop using array:wish to store array values from loop for use outside loop

Here's my code: awk -F '' 'NR==FNR { if (/time/ && $5>10) A=$2" "$3":"$4":"($5-01) else if (/time/ && $5<01) A=$2" "$3":"$4-01":"(59-$5) else if (/time/ && $5<=10) A=$2" "$3":"$4":0"($5-01) else if (/close/) { B=0 n1=n2; ... (2 Replies)
Discussion started by: klane
2 Replies

6. Shell Programming and Scripting

awk loop and using shell in awk

Hi, everyone! I have a file, when I print its $1 out it show several strings like this: AABBCC AEFJKLFG FALEF FAIWEHF What I want to do is that, after output of each record, search the string in all files in the same folder, print out the record and file name. This is what I want... (4 Replies)
Discussion started by: xshang
4 Replies

7. Shell Programming and Scripting

awk - loop from a to z

Hello, I was wondering if it is possible to do a loop on letters rather than numbers with awk (gawk). Basically I used to do: echo "nothing" | gawk '{for(i=1;i<11;i++)print i}' But I would like to do something like that (which obviously does not work): echo "nothing" | gawk '{for(i in... (6 Replies)
Discussion started by: jolecanard
6 Replies

8. Shell Programming and Scripting

Comparison and editing of files using awk.(And also a possible bug in awk for loop?)

I have two files which I would like to compare and then manipulate in a way. File1: pictures.txt 1.1 1.3 dance.txt 1.2 1.4 treehouse.txt 1.3 1.5 File2: pictures.txt 1.5 ref2313 1.4 ref2345 1.3 ref5432 1.2 ref4244 dance.txt 1.6 ref2342 1.5 ref2352 1.4 ref0695 1.3 ref5738 1.2... (1 Reply)
Discussion started by: linuxkid
1 Replies

9. Shell Programming and Scripting

awk for-loop and NR

Hey, I know this is a stupid question, but it doesn't work. I have a file with 10 lines and I want to pipe the content to awk and then print line 1 til 2 into another file and then line 3-4 ... So my script looks like that, but doesn't work: cat grid_ill.pts | awk '{ for (NR=1;NR<3;NR++)... (8 Replies)
Discussion started by: ergy1983
8 Replies

10. UNIX for Dummies Questions & Answers

for loop in awk?

I am new to unix and have pieced together two scripts that work independently. The first checks all the filesystems and reports which are running low on space. df -m | awk 'int($4) > 75 { print $1 " has only " $3 "mb free from a total of " $2 ", this filesystem is " $4 " full! \n" }... (1 Reply)
Discussion started by: Bdawk
1 Replies
Login or Register to Ask a Question