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Edit first line of a text file


 
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# 1  
Old 08-29-2012
Edit first line of a text file

Hi friends,

Issue1:

I have a text file with the first line like this

Code:
#chrom	start	end	Readcount_A	Normalized_Readcount_A	ReadcountB	Normalized_Readcount_B	Fc_A_vs_B	pvalue_A_vs_B	FDR_A_vs_B	Fc_B_vs_A	pvalue_B_vs_A	FDR_B_vs_A	<a href="http://unix.com/">Link</a>

How can I change it to the following without opening the file?

Code:
#chrom	start	end	Readcount_KO	Normalized_Readcount_KO	Readcount_WT	Normalized_Readcount_WT	Fc_KO_vs_WT	pvalue_KO_vs_WT	FDR_KO_vs_WT	Fc_WT_vs_KO	pvalue_WT_vs_KO	FDR_WT_vs_KO	Link

Issue2:

How do I add the below line to a text file as a first line?

Code:
#chrom	start	end	Readcount_KO	Normalized_Readcount_KO	Readcount_WT	Normalized_Readcount_WT	Fc_KO_vs_WT	pvalue_KO_vs_WT	FDR_KO_vs_WT	Fc_WT_vs_KO	pvalue_WT_vs_KO	FDR_WT_vs_KO	Link

I am looking for something in awk. Thanks in advance.
# 2  
Old 08-29-2012
Why awk? What have you tried so far?

You always have to open a file, wether for reading, writing or both, afaik. Maybe you mean something else instead of "open".

Issue 2:
Write the line to a file and add the long file to the one-liner file by shell's redirection/concatenation.
# 3  
Old 08-29-2012
Hello,
You can try this:
Quote:
echo "#chrom start end Readcount_KO Normalized_Readcount_KO Readcount_WT Normalized_Readcount_WT Fc_KO_vs_WT pvalue_KO_vs_WT FDR_KO_vs_WT Fc_WT_vs_KO pvalue_WT_vs_KO FDR_WT_vs_KO Link" > file
with ">>" append this to the file and whit ">" remove the content of the file.
This User Gave Thanks to mauregato For This Post:
# 4  
Old 08-29-2012
use sed to replace without opening file .
# 5  
Old 08-29-2012
Quote:
Originally Posted by gagandeep
use sed to replace without opening file .
Nothing can edit a file without opening it. Files don't work that way.
# 6  
Old 08-29-2012
Code:
 
sed 's/A/KO/g' > corona688.txt

it will change the text without opening the file.

or you can use
Code:
 
sed -i 's/A/KO/g'

this will save in the current file.
This User Gave Thanks to gagandeep For This Post:
# 7  
Old 08-29-2012
Quote:
Originally Posted by gagandeep
Code:
 
sed 's/A/KO/g' > corona688.txt

it will change the text without opening the file.
I see. Something else had to open it in the first place, however, if not reading from stdin.
Quote:
or you can use
Code:
 
sed -i 's/A/KO/g'

this will save in the current file.
It does NOT save it in the current file. It deletes the file and creates a new one. This can have bad effects on file ownership and permissions.
This User Gave Thanks to Corona688 For This Post:

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