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Shell Programming and Scripting

Reversing a line based on column

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# 1  
Old 11-30-2009
Reversing a line based on column
Hi,

I have a file that looks like this (tab seperated):

Code:
read   -  DFHJ
read1 -  IOPE
read2 + AAAB
read3 + MMMN

Basically what i want to do is reverse column 3 if column 2 has a - but leave it if its +

so the output would look like this:

Code:
read   -  JHFD
read1 -  EPOI
read2 + AAAB
read3 + MMMN

I am able to use awk to reverse individual lines but I cannot do it according to a particular column. thanks

Smilie
# 2  
Old 11-30-2009
Code:
 awk 'function rev(str){ tmp=""; for(i=length(str);i>0;i--)
                                    {tmp=tmp substr(str,i,1)} 
                                 return tmp}
      {print $1, $2, ($2=="-") ? rev($3) : $3}  '  filename > newfilename

# 3  
Old 11-30-2009
With Perl:

Code:
perl -ape'
  s/(-\s*)(\w+)/$1.reverse$2/e
  ' infile

# 4  
Old 11-30-2009
Quote:
Originally Posted by jim mcnamara
Code:
 awk 'function rev(str){ tmp=""; for(i=length(str);i>0;i--)
                                    {tmp=tmp substr(str,i,1)} 
                                 return tmp}
      {print $1, $2, ($2=="-") ? rev($3) : $3}  '  filename > newfilename

nice function, especially this line:

tmp=tmp substr(str,i,1)
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