Get length of longest line in a file

StackOverflow https://stackoverflow.com/questions/1655372

  •  11-09-2019
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Question

I'm looking for a simple way to find the length of the longest line in a file. Ideally, it would be a simple bash shell command instead of a script.

Was it helpful?

Solution

Using wc (GNU coreutils) 7.4:

wc -L filename

gives:

101 filename

OTHER TIPS

awk '{print length, $0}' Input_file |sort -nr|head -1

For reference : Finding the longest line in a file

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

Just for fun and educational purpose, the pure POSIX shell solution, without useless use of cat and no forking to external commands. Takes filename as first argument:

#!/bin/sh

MAX=0 IFS=
while read -r line; do
  if [ ${#line} -gt $MAX ]; then MAX=${#line}; fi
done < "$1"
printf "$MAX\n"

wc -L < filename

gives

101

perl -ne 'print length()."  line $.  $_"' myfile | sort -nr | head -n 1

Prints the length, line number, and contents of the longest line

perl -ne 'print length()."  line $.  $_"' myfile | sort -n

Prints a sorted list of all lines, with line numbers and lengths

. is the concatenation operator - it is used here after length()
$. is the current line number
$_ is the current line

Important overlooked point in the above examples.

The following 2 examples count expanded tabs

  wc -L  <"${SourceFile}" 
# or
  expand --tabs=1 "${SourceFile}" | awk '{ if (length($0) > max) {max = length($0)} } END { print max }'

The following 2 count non expaned tabs.

  expand --tabs=1 "${SourceFile}" | wc -L 
# or
  awk '{ if (length($0) > max) {max = length($0)} } END { print max }' "${SourceFile}"

so 

              Expanded    nonexpanded
$'nn\tnn'       10            5

Looks all the answer do not give the line number of the longest line. Following command can give the line number and roughly length:

$ cat -n test.txt | awk '{print "longest_line_number: " $1 " length_with_line_number: " length}' | sort -k4 -nr | head -3
longest_line_number: 3 length_with_line_number: 13
longest_line_number: 4 length_with_line_number: 12
longest_line_number: 2 length_with_line_number: 11

In perl:

perl -ne 'print ($l = $_) if (length > length($l));' filename | tail -1

this only prints the line, not its length too.

Here are references of the anwser

cat filename | awk '{print length, $0}'|sort -nr|head -1

http://wtanaka.com/node/7719

Just for fun, here's the Powershell version:

cat filename.txt | sort length | select -last 1

And to just get the length:

(cat filename.txt | sort length | select -last 1).Length

I'm in a Unix environment, and work with gzipped files that are a few GBs in size. I tested the following commands using a 2 GB gzipped file with record length of 2052.

  1. zcat <gzipped file> | wc -L

and

  1. zcat <gzipped file> | awk '{print length}' | sort -u

The times were on avarage

  1. 117 seconds

  2. 109 seconds

Here is my script after about 10 runs.

START=$(date +%s) ## time of start

zcat $1 |  wc -L

END=$(date +%s) ## time of end
DIFF=$(( $END - $START ))
echo "It took $DIFF seconds"

START=$(date +%s) ## time of start

zcat $1 |  awk '{print length}' | sort -u

END=$(date +%s) ## time of end
DIFF=$(( $END - $START ))
echo "It took $DIFF seconds"

Variation on the theme.

This one will show all lines having the length of the longest line found in the file, retaining the order they appear in the source.

FILE=myfile grep `tr -c "\n" "." < $FILE | sort | tail -1` $FILE

So myfile

x
mn
xyz
123
abc

will give

xyz
123
abc
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