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deepblue_86
Asked: 2015-10-21 02:57:38 +0800 CST

creating loop over the lines of text files

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i is an integer (lets say 4). I have three text files (a,b,c) contain single lines with strings, total number of lines of files equal to i (4). For example "a" file contains;

trm320
abc000
dfg1002
der5205

I need to create the output (on the screen or in the text file) with loop like;

a(1) b(1) c(1) (first line of a,b,c files)

a(4) b(4) c(4) (last line of a,b,c files)

What kind of loop do I need to create?

scripts

1 Answers

  1. Best Answer

    paste does exactly what you want.

    DESCRIPTION
       Write  lines  consisting  of  the sequentially corresponding lines from
       each FILE, separated by TABs, to standard output.   With  no  FILE,  or
       when FILE is -, read standard input.

       Mandatory  arguments  to  long  options are mandatory for short options
       too.

       -d, --delimiters=LIST
              reuse characters from LIST instead of TABs

    In your case

    paste -d " " a b c

    will do the trick. If you need the output in a file, redirect >output the output.

    To access the n-th line of a file, use sed. For convenience wrap it up in a Bash function (pl is supposed to mean Print Line)

    function pl {
  sed -n "$1p" $2
}

    Calling for example pl 5 a will print the fifth line of file a. To store it in a variable 

    fifth=$(pl 5 a)

    or combine both tasks

    paste a b c | pl 5 -

    to print the fifth line of the concatenated file.

    To get a file into an array, use mapfile, from this answer:

    mapfile -t myArray < output.txt
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