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How to read only 1st three character from a file using sed in unix


 
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# 1  
Old 08-15-2009
How to read only 1st three character from a file using sed in unix

Hi
can any one please help me how to read forst three character from a file using sed or any other way

example

My file contains data like this

asd123#412

I want to just read 1st three characters no matter whatever it is (character, digit, special characters, space, tab..etc)

Thanks in advance
# 2  
Old 08-15-2009
Code:
[house@leonov] FULL='asd123#412' ; PART=${FULL:0:3} ; echo $PART
asd

# 3  
Old 08-15-2009
Code:
sed 's/\(.\{3\}\).*/\1/' file

# 4  
Old 08-15-2009
Why can you not use cut?
Code:
cut -c1-3  filename

Sounds like homework to me.....
# 5  
Old 08-15-2009
Few more:

Code:
awk '{print substr($0,1,3)}' file

perl -lne '/(.{3}).*/ and print $1' file

perl -lne '/(...).*/ and print $1' file

perl -lne 'print substr($_,0,3)' file

perl -lne '@x=unpack("A3"); print $x[0]' file

tyler_durden
# 6  
Old 08-16-2009
Quote:
Originally Posted by danmero
Code:
sed 's/\(.\{3\}\).*/\1/' file

Thank u very much,

Can u pls throw some light over it.
# 7  
Old 08-16-2009
Taking this task literally, any program which knows about records is not suitable. We need to read the raw file.

My solution to getting the first three characters of a file no matter what they are is:

Code:
dd bs=3 count=1 if=input_file of=output_file

We have avoided putting the characters in a shell variable because we don't know what they are.
Program "cut" is unsuitable if one of the characters is a linefeed for example.

Last edited by methyl; 08-16-2009 at 11:24 AM.. Reason: several typos!

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