Ytukyg

can anyone give a look to this bash script of mine please? I am trying to find the longest line in a file using a bash script so I wrote this.

#!/bin/bash



#Francesco Foschi length of a row in a file



let n=0

let max_length=0



while read row

do

    length=$(echo -n $row | wc -c)

    if[ ${#length} -gt ${#max_length} ]

    then

            let max_length=${#length}

    fi



    echo "$n row is $length charachters long"

    echo "$row"

    let n=n+1



done < $1



echo "longest line is $max_length charachters long"



exit 0

Every time I try to run the console says that I have a syntax error near the unexpected then token. What am I doing wrong??

BTW running of fedora28

try this:

#!/bin/bash

#Francesco Foschi length of a row in a file



let n=0

let max_length=0



while read row

do

    length=$(echo -n $row | wc -c)

    if [ ${length} -gt ${max_length} ]

    then

            let max_length=${length}

    fi



    echo "$n row is $length charachters long"

    echo "$row"

    let n=n+1



done < $1



echo "longest line is $max_length charachters long"



exit 0

GNU wc has this functionality built in:

-L, --max-line-length

        print the maximum display width

plain bash

#!/bin/bash

max=-1

while IFS= read -r line; do

    [[ ${#line} -gt $max ]] && max=${#line}

done < "$1"

echo "longest line is $max chars long"

This idiom is used to read the line exactly verbatim: IFS= read -r line

Demo:

1. 
   

   create a file with leading/trailing whitespace and a backslash

   
   
   

   $ echo ' hbHello ' > file
   
   

   
   
   

   this file is 10 bytes in size (not counting the trailing newline).

   
   


2. 
   

   read it with plain read var

   
   
   

   $ read line < file; printf %s "$line" | od -c
   
   0000000   h   b   H   e   l   l   o
   
   0000007
   
   

   
   
   

   Only 7 chars: missing the backslash and the whitespace

   
   


3. 
   

   add the -r option for read:

   
   
   

   $ read -r line < file; printf %s "$line" | od -c
   
   0000000   h      b   H   e   l   l   o
   
   0000010
   
   

   
   
   

   Now we have 8 characters (the "0000010" is octal), but still missing the whitespace.

   
   


4. 
   

   add the IFS= variable assignment:

   
   
   

   $ IFS= read -r line < file; printf %s "$line" | od -c
   
   0000000       h      b   H   e   l   l   o    
   
   0000012
   
   

   
   
   

   10 characters (octal 12): now we have exactly what was written to the file in $line.

   
   

It's a pain to have to write IFS= read -r line all the time, but bash inflicts considerable pain on the programmer.