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

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 b开发者_开发技巧e 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.

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?

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.

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

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.

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.

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! :-)

You could combine your original ideas:

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

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

Use a shell variable to pass the result from one script to another, using awk's -v argument parsing

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

awk -v max=$MAX 'length <= max { printf "%-"max"sX\n",$0 }' in.txt

OR you could replace the hard-coded 50 with shell $() command substitution to create this ugly one-line beast:

awk -v max=$(awk '{ if (length($0) > max){max = length($0)} } END { print max }' in.txt) 'length <= max { printf "%-"max"s\n",$0 }' in.txt