Find Longest Line in a .txt File and fill all Lines to that Length with 'blank Spaces'?

Question

How can I find the longest line in a .txt file and then fill all other lines at their end to that length with blank spaces?

My guess is this is easy to answer. I know very little about using the awk, paste command and such. Maybe someone can help me out. Thanks!

A little more specific... so far I can do the following. This would get the longest Line from a .txt File:

awk '{ if (length($0) > max) {max = length($0); maxline = $0} } END { print maxline }' in.txt

This fills the lines with blank spaces (till 50):

awk  'length <= 50 { printf "%-50s\n",$0 }' in.txt > out.txt

I just don't know to pass the value from one line to the other.

Why am I asking this? I want to merge two .txt files using the paste command. Text B will be positioned to the right of Text A. Lines in Text A will have different lengths. So if there are not enough blank spaces the layout isn't right.

Answer 1

You can use wc to count the number of characters in a line. Measure all lines in the file to find the longest length. For all other files, (max length - line length) gives you the number of space characters to print at the end of the line (which you can do with printf).

Update: Is using awk a requirement? If not, try this:

# Measure the longest line in the file
maxlen=`wc -L filename.txt | cut -d ' ' -f 1`

# Pad each line to $maxlen characters
while read line
do
    printf "%-${maxlen}s\n" "$line" >> outfile.txt
done < filename.txt

Edit #2: If you don't have the -L option to wc, you can calculate the length of the longest line using the following loop:

maxlen=0
while read line
do
    thislen=`echo $line | wc -c`
    [ $[$thislen>$maxlen] ] && maxlen=$thislen
done < filename.txt

The ending value of $maxlen will be the length of the longest line.

Answer 2

wc -L or wc --max-line-length computes and displays the length of the longest line in the input (may not be available on all versions of wc).

---

With the max line length in some variable (say, $max), run

while read line
do
    printf "%-${max}s\n" $line
done < in.txt > out.txt

Answer 3

If 'shell scripting' can include Python scripts, something like this:

maxLen = 0
infile = open("file.txt", 'r')
outfile = open("out.txt", 'w')
for line in infile:
    if len(line)>maxLen: maxLen = len(line)
infile.seek(0)
for line in infile:
    rawline = line.strip('\r\n')
    out.write (rawline + ''.join([' ' for i in range(maxLen-len(rawline))]) + "\n")
infile.close ()
outfile.close ()

Fixing any off-by-one errors is left as an exercise for the reader! :-)

Answer 4

Usually I find that this type of question is a result of this thought process:

1. I am trying to solve problem A
2. I think doing process B will solve A
3. I will ask how to achieve process B

You will get literal answers on how to achieve process B - but if you include the context of problem A, you will get better answers and probably one that solves problem A in a simpler manner than process B.

So, what problem are you trying to solve by making all the lines in a file the same length?

Answer 5

This is all you need:

pr  -W 80 -mtT file1 file2

Or, more verbosely:

pr --page-width=80 --merge --omit-header --omit-pagination file1 file2

Vary the number to change the layout of the result.

Answer 6

here's how one way to it with just awk.

$ more file
jlsf
slf
asdfasfs
sd

$ awk 'FNR==NR{t=(length>=t)?length:t;next}length<t{for(o=1;o<=t-length;o++)s=s "|";$0=$0s;s=""}1' file file
jlsf||||
slf|||||
asdfasfs
sd||||||

Change "|" to spaces as desired.