Display two files side by side

Question

How can 2 unsorted text files of different lengths be display side by side (in columns) in a shell

Given one.txt and two.txt:

$ cat one.txt
apple
pear
longer line than the last two
last line

$ cat two.txt
The quick brown fox..
foo
bar 
linux

skipped a line

Display:

apple                               The quick brown fox..
pear                                foo
longer line than the last two       bar 
last line                           linux

                                    skipped a line

paste one.txt two.txt almost does the trick but doesn't align the columns nicely as it just prints one tab between column 1 and 2. I know how to this with emacs and vim but want the output displayed to stdout for piping ect.

The solution I came up with uses sdiff and then pipes to sed to remove the output sdiff adds.

sdiff one.txt two.txt | sed -r 's/[<>|]//;s/(\t){3}//'

I could create a function and stick it in my .bashrc but surely a command for this exists already (or a cleaner solution potentially)?

Solution 1

You can use pr to do this, using the -m flag to merge the files, one per column, and -t to omit headers, eg.

pr -m -t one.txt two.txt

outputs:

apple                               The quick brown fox..
pear                                foo
longer line than the last two       bar
last line                           linux

                                    skipped a line

See Also:

• Print command result side by side
• Combine text files column-wise

Solution 2

To expand a bit on @Hasturkun's answer: by default pr uses only 72 columns for its output, but it's relatively easy to make it use all available columns of your terminal window:

pr -w $COLUMNS -m -t one.txt two.txt

Most shells will store (and update) your terminal's screenwidth in the $COLUMNS shell variable, so we're just passing that value on to pr to use for its output's width setting.

This also answers @Matt's question:

Is there a way for pr to auto-detect screen width?

So, no: pr itself can't detect the screenwidth, but we're helping it out a bit by passing in the terminal's width via its -w option.

Note that $COLUMNS is a shell variable, not an environment variable, so it isn't exported to child processes, and hence the above approach will likely not work in scripts, only in interactive TTYs... see LINES and COLUMNS environmental variables lost in a script for alternative approaches.

Solution 3

If you know the input files have no tabs, then using expand simplifies @oyss's answer:

paste one.txt two.txt | expand --tabs=50

If there could be tabs in the input files, you can always expand first:

paste <(expand one.txt) <(expand two.txt) | expand --tabs=50

Solution 4

paste one.txt two.txt | awk -F'\t' '{
    if (length($1)>max1) {max1=length($1)};
    col1[NR] = $1; col2[NR] = $2 }
    END {for (i = 1; i<=NR; i++) {printf ("%-*s     %s\n", max1, col1[i], col2[i])}
}'

Using * in a format specification allows you to supply the field length dynamically.

Solution 5

There is a sed way:

f1width=$(wc -L <one.txt)
f1blank="$(printf "%${f1width}s" "")"
paste one.txt two.txt |
    sed "
        s/^\(.*\)\t/\1$f1blank\t/;
        s/^\(.\{$f1width\}\) *\t/\1 /;
    "

Under bash, you could use printf -v:

f1width=$(wc -L <one.txt)
printf -v f1blank "%${f1width}s"
paste one.txt two.txt |
    sed "s/^\(.*\)\t/\1$f1blank\t/;
         s/^\(.\{$f1width\}\) *\t/\1 /;"

_{(Of course @Hasturkun 's solution pr is the most accurate!)}:

Advantage of sed over pr

You can finely choose separation width and or separators:

f1width=$(wc -L <one.txt)
(( f1width += 4 ))         # Adding 4 spaces
printf -v f1blank "%${f1width}s"
paste one.txt two.txt |
    sed "s/^\(.*\)\t/\1$f1blank\t/;
         s/^\(.\{$f1width\}\) *\t/\1 /;"

Or, for sample, to mark lines containing line:

f1width=$(wc -L <one.txt)
printf -v f1blank "%${f1width}s"
paste one.txt two.txt |
    sed "s/^\(.*\)\t/\1$f1blank\t/;
  /line/{s/^\(.\{$f1width\}\) *\t/\1 |ln| /;ba};
         s/^\(.\{$f1width\}\) *\t/\1 |  | /;:a"

will render:

apple                         |  | The quick brown fox..
pear                          |  | foo
longer line than the last two |ln| bar 
last line                     |ln| linux
                              |  | 
                              |ln| skipped a line

View more solutions

Comments

[fedorqui]

Not in a shell, but worth mentioning: use meld!

[Chris Seymour]

Perfect! Knew something would exist, never heard of pr before. I tried with 3 files and the output was truncated but the -w option solved that. Nice answer.

[Hasturkun]

@sudo_o: Happy to help, coreutils is full of gems

[Chris Seymour]

sdiff is diff -y which I discuss in the question.

[Vikas Jain]

Yes right... it was mentioned to show another command/flag setting of doing it.

[Chris Seymour]

But it doesn't answer the questions diff adds characters between the two files.

[Matt]

Is there a way for pr to auto-detect screen width?

[Hasturkun]

@Matt: You could use $COLUMNS, which should be provided by the shell.

[molnarg]

When used to print two files side by side, pr cuts the end of long lines. Is there a way to make it wrap the lines?

[crw]

@molnarg: One method is to first fold each input file to half the page width, less any column-separator width. EG, in bash: pr -t -m -w $PAGE_WIDTH <(fold -w $HALF_PAGE_WIDTH one.txt) <(fold -w $HALF_PAGE_WIDTH two.txt). This could be solved elegantly in user-created script.

[Ashutosh Baheti]

Is there a way to show 1 line from first file and 10 lines from the second file? Its machine translation outputs that I want to view side by side.

[Lichtgestalt]

pr -mtJ ... to use all available width.

[alper]

can I apply this for output of two processes instead of a file?

[Jishnu P Das]

bash f1width=$(wc -L <one.txt) printf -v f1blank "%${f1width}s" paste one.txt two.txt | sed "s/^\(.*\)\t/\1$f1blank\t/; /line/{s/^\(.\{$f1width\}\) *\t/\1 |ln| /;ba}; s/^\(.\{$f1width\}\) *\t/\1 | | /;:a" Nice solution!! really helpful in other contexts

[Graham Toal]

Thanks for the hints here. I've used it in a bash script: pr -m -t -w$((2 * $(cat $1 $2|wc -L))) $1 $2