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Redirect output to the same input file in awk

 
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# 1  
Old 02-25-2015
Redirect output to the same input file in awk
Hi,

I want to compare a value from test file and redirect the o/p value to the same file

Code:
input file
250     32000   32      128

Below is my code
Code:
 
awk '{ if ($1 < "300") print $1 > /tmp/test}' test

want to compare 250 < 300 then print 300 to the same place

below is the required output
Code:
 
output file
300     32000   32      128

But the value (300) is not updating
# 2  
Old 02-25-2015
Hello Stew,

Following may help you in same, following code will check if field 1st is less than 300 then it will print 300 at first field else it will print actual 1st field's values.
Code:
awk '{$1=$1<300?300:$1} 1'  Input_file

Output will be as follows.
Code:
300 32000 32 128

Also you can redirect this to a output file as per your requirement too.


Thanks,
R. Singh
# 3  
Old 02-25-2015
Code:
awk '{ if ($1 < "300") { sub($1,"300",$0); print > "/tmp/test" } }' /tmp/test

This User Gave Thanks to anbu23 For This Post:
stew
# 4  
Old 02-25-2015
Anbu -Thanks, your code is working. But I don't understand
Code:
sub ($1,"300"$0)

why you used $0 in target. I know sub will return either 0 or 1. I am bit confused.
# 5  
Old 02-25-2015
sub($1,"300",$0) - Sub() replaces first field by 300 in $0 (entire line read from file test)
This User Gave Thanks to anbu23 For This Post:
stew
# 6  
Old 02-25-2015
Anbu - your work for single line below is my actual i/p and o/p file

Code:
kernel.sem = 250   32000   32      128250
kernel.small = 1612364
kernel.shmmax = 2147483648

when I run
Code:
awk '/kernel.sem/ { if ($3 < "300") { sub($3,"300",$0); print > "/tmp/test" } }' /tmp/test

the entire file is replaced like below
Code:
kernel.sem = 300   32000   32      128250

my actual o/p file should be

Code:
kernel.sem = 300   32000   32      128250
kernel.small = 1612364
kernel.shmmax = 2147483648

if I run
Code:
awk '/kernel.sem/ {print $3,$6}' /tmp/test

, it prints
Code:
300 128250

correctly
# 7  
Old 02-25-2015
Hello Stew,

Could you please try following and let me know if this helps.
Also my solution in POSt#2 also may help you in same.
Code:
awk '/kernel.sem/ { if ($3 < "300") { sub($3,"300",$0); print >> "/tmp/test1" } else {print >> "/tmp/test1" }}' /tmp/test

Here I am creating /tmp/test1 file as output, because file named /tmp/test is input file.

Hope this helps.

Thanks,
R. Singh
 
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