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I have the following two files ( I padded the lines with dots so every line in a file is the same width and made file1 all caps to make it more clear).

contents of file1:


contents of file2


Notice that file2 is longer than file1.

When I run this command:

paste file1 file2

I get this output

ETIAM...... Lorem....
SED........ Proin....
MAECENAS... Nunc.....
DONEC...... Quisque..

What can I do for the output to be as follows ?

ETIAM...... Lorem....
MAECENAS... Nunc.....
DONEC...... Quisque..

I tried

paste file1 file2 | column -t

but it does this:

ETIAM......  Lorem....
MAECENAS...  Nunc.....
DONEC......  Quisque..

non as ugly as original output but wrong column-wise anyway.

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paste is using tabs in front of the lines from second file. You may have to use a postprocessor to align the columns appropriately. –  unxnut Nov 5 '13 at 14:17
paste file1 file2 | column -tn ? –  ninjalj Nov 5 '13 at 14:18
does file1 always have fixed size columns? –  RSFalcon7 Nov 5 '13 at 14:18
@ninjalj That solved it. Write an answer so I can accept it. –  user1598390 Nov 5 '13 at 15:17
@RSFalcon7 Yes, it does. –  user1598390 Nov 6 '13 at 0:42

5 Answers 5

up vote 9 down vote accepted

Assuming you don't have any tab characters in your files,

paste file1 file2 | expand -t 13

with the arg to -t suitably chosen to cover the desired max line width in file1.

Added by OP:

I did this so it works without the magic number 13:

paste file1 file2 | expand -t $((`wc -L file1|awk '{print $1}'` + 2))

It's not easy to type but can be used in a script.

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I thought awk might do it nicely, so I googled "awk reading input from two files" and found an article on stackoverflow to use as a starting point.

First is the condensed version, then fully commented below that. This took a more than a few minutes to work out. I'd be glad of some refinements from smarter folks.

awk '{if(length($0)>max)max=length($0)}
END { format = "%-" max "s\t%-" max "s\n";
  for (i=1; i<=numlines; i++) { printf format, s1[i]?s1[i]:"", s2[i]?s2[i]:"" }
}' file1 file2

And here is the fully documented version of the above.

# 2013-11-05 mike@diehn.net
# Invoke thus:
#   awk -f this_file file1 file2
# The result is what you asked for and the columns will be
# determined by input file order.
# No matter which file we're reading,
# keep track of max line length for use
# in the printf format.

# FNR is record number in current file
# NR is record number over all
# while they are equal, we're reading the first file
#   and we load the strings into array "s1"
#   and then go to the "next" line in the file we're reading.
FNR==NR { s1[FNR]=$0; next }

# and when they aren't, we're reading the
#   second file and we put the strings into
#   array s2

# At the end, after all lines from both files have
# been read,
  # use the max line length to create a printf format
  # the right widths
  # and figure the number of array elements we need
  # to cycle through in a for loop.
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Not a very good solution but I was able to do it using

paste file1 file2 | sed 's/^TAB/&&/'

where TAB is replaced with the tab character.

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What is the role of && in the sed command? –  coffeMug Nov 5 '13 at 14:57
A single & puts what is being searched for (a tab in this case). This command simply replaces the tab at the beginning with two tabs. –  unxnut Nov 5 '13 at 15:59
I had to change TAB to \t to make this work in zsh on Ubuntu debian. And it does only work if file1 has less than 15 chars –  rubo77 Nov 30 '13 at 6:53

On Debian and derivatives, column has a -n nomerge option that allows column to do the right thing with empty fields. Internally, column uses the wcstok(wcs, delim, ptr) function, which splits a wide character string into tokens delimited by the wide characters in the delim argument.

wcstok starts by skipping wide characters in delim, before recognizing the token. The -n option uses an algorythm that doesn't skip initial wide-characters in delim.

Unfortunately, this isn't very portable: -n is Debian-specific, and column is not in POSIX, it's apparently a BSD thing.

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An awk solution that should be fairly portable, and should work for an arbitrary number of input files:

# Invoke thus:
#   awk -F\\t -f this_file file1 file2

# every time we read a new file, FNR goes to 1

FNR==1 {
    curfile++                       # current file

# read all files and save all the info we'll need
    column[curfile,FNR]=$0          # save current line
    nlines[curfile]++               # number of lines in current file
    if (length > len[curfile])
            len[curfile] = length   # max line length in current file

# finally, show the lines from all files side by side, as a table
    # iterate through lines until there are no more lines in any file
    for (line = 1; !end; line++) {
            $0 = _
            end = 1

            # iterate through all files, we cannot use
            #   for (file in nlines) because arrays are unordered
            for (file=1; file <= curfile; file++) {
                    # columnate corresponding line from each file
                    $0 = $0 sprintf("%*s" FS, len[file], column[file,line])
                    # at least some file had a corresponding line
                    if (nlines[file] >= line)
                            end = 0

            # don't print a trailing empty line
            if (!end)
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How do you use this on file1 and file2? I called the script paste-awk and tried paste file1 file2|paste-awk and I tried awk paste-awk file1 file2 but none worked. –  rubo77 Nov 30 '13 at 7:04
I get awk: Line:1: (FILENAME=file1 FNR=1) Fatal: Division by zero –  rubo77 Nov 30 '13 at 7:04
@rubo77: awk -f paste-awk file1 file2 should work, at least for GNU awk and mawk. –  ninjalj Dec 2 '13 at 10:32
This works, although it is slightly different from paste there is less space between the two rows. And if the input file has not all rows same length, it will result in an align-right row –  rubo77 Dec 2 '13 at 14:14
@rubo77: the field separator can be set with -F\\t –  ninjalj Dec 2 '13 at 15:30

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