bash text to variable accessing individual text lines

patolfo · 05-02-2010, 12:27 PM

Hi there guys, i am on processing text tasks
And i found that if you assign a text to a variable is chomp'ed automatically the newline

Code:

variable=$(cat file.txt)

The problem is i can only access the items/lines using:

Code:

for line in $variable
do
echo $line
# Other commands
done

Question is, how do i convert this to an indexed array. More importantly, how do i get access to individual $line[0], ..., $line[n]

Another thing, if the file.txt, has lines with spaces it is a mess using the for...in..., but echoing prints line by line...o_0

PTrenholme · 05-02-2010, 01:18 PM

Try something like this:

Code:

i=0
while read line[$i]
do
  i=$(($i+1))
done < file.txt

See info bash for details re read and input redirection.

grail · 05-02-2010, 10:51 PM

Above works fine, but you may also need to ask your self are you using the right tools, ie if you are traversing an entire file to make changes to certain lines
then maybe you should be using sed or awk or maybe even doing it in Perl.

Another alternative to yours which is reacting the IFS variable is to change it:

Code:

OLD=$IFS
IFS=$'\n'
variable=($(cat file))

<for loop>
IFS=$OLD

patolfo · 05-03-2010, 09:57 AM

Well i must admit i did not know about IFS

But it is helpful, to ask here

I will give ti a shot with IFS...

Thanks guys!

patolfo · 05-03-2010, 10:22 AM

This is my code:

Code:

#!/bin/bash

sipo=$(cat si_pregunta_por_mi)
OLD=$IFS
IFS=$'\n'

#for line in $sipo
#do
#echo $line
#done
echo "$sipo[1]"

IFS=$OLD
exit

I tried to print only one line, can it be done?

Code:

Lorem ipsum

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Vivamus vel lectus arcu, sed lobortis odio.
Nunc tempor dolor tortor, nec consectetur massa.
Phasellus et eros non nisl posuere posuere at ac nibh.
Integer fermentum neque non libero sodales sodales.[1]

This is the input text:

Code:

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Vivamus vel lectus arcu, sed lobortis odio.
Nunc tempor dolor tortor, nec consectetur massa.
Phasellus et eros non nisl posuere posuere at ac nibh.
Integer fermentum neque non libero sodales sodales.

grail · 05-03-2010, 10:41 AM

Close just a small change

Code:

OLD=$IFS
IFS=$'\n'
sipo=$(cat si_pregunta_por_mi)

<do your tests now>

petrus4 · 05-05-2010, 12:00 PM

Quote:

Originally Posted by patolfo

I tried to print only one line, can it be done?

Code:

Lorem ipsum

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Vivamus vel lectus arcu, sed lobortis odio.
Nunc tempor dolor tortor, nec consectetur massa.
Phasellus et eros non nisl posuere posuere at ac nibh.
Integer fermentum neque non libero sodales sodales.[1]

Code:

sed -n '1p' <file.txt>

The above will print one line. Also...

Code:

head -n5 <file.txt>

The above will print the first five lines, and

Code:

tail -n5 <file.txt>

this will print the last five.

patolfo · 05-06-2010, 09:53 AM

the problem is that i want to print it like

Code:

echo ${line[5]}

and expecting the whole line,
this is accessing the text as an array basically, but thanks for your comment

catkin · 05-06-2010, 12:13 PM

This should do the trick

Code:

#!/bin/bash

# Read file into array lines, one line per array element
while read line
do
    lines+=( "$line" )
done < <(cat input.txt)

# See if it worked
for (( i=0; i< ${#lines[*]}; i++ ))
do
    echo "${lines[i]}"
done

PTrenholme · 05-10-2010, 04:46 PM

As I said in post #2, above, a simple done < input.txt does the trick.

The addition of the <(cat input.txt) is unnecessary unless you're using the cat command for additional input processing (which is not indicated in the proposed command).

catkin · 05-11-2010, 01:26 AM

Quote:

Originally Posted by PTrenholme

As I said in post #2, above, a simple done < input.txt does the trick.

The addition of the <(cat input.txt) is unnecessary unless you're using the cat command for additional input processing (which is not indicated in the proposed command).

Good point, thanks

patolfo · 05-11-2010, 10:21 AM

Thanks a lot Catkin, it finally worked