Output numbers from a file in a different order

Question

I have a file that contains:

1 2 3 4
1 3 5 4 8
3 2 1 

Each line has a different number of digits. And there are 1000 more like this.

I want the output like this:

1 2
2 3
3 4
4 0
1 3
3 5
5 4
4 8
8 0
3 2
2 1
1 0

edit made to this post!!

i mean if this is last digit in line put that digit and then zero besides it.

for example if digit is last in that line we put in output new line that digit and zero

4 0 and others:see output sample tnx

in above example and

How can I do that, in perl awk or bash

i use this but its not working :((

awk '{
for (i=1; i<NF; i++)
{
if ( $(i+1) == "")
print $i, "0"
else
print $i, $(i+1)
}
}' UniqASinline> inTestAst

the outpute file of Mr.glenn jackman way:

for this imput:

3549 
3549 10026 
3549 10026 10010 
3549 10026  
awk '{for (i=1; i<=NF; i++) printf("%d %d\n", $i, $(i+1))}' filename

3549 
3549 10026
10026 
3549 10026
10026 10010
10010 
3549 10026
10026

but we expect:

3549 0
3549 10026
10026 0
3549 10026
10026 10010
10010 0
3549 10026
10026 0

tnx

Answer 1

awk '{for (i=1; i<NF; i++) print $i, $(i+1)}' filename

EDIT: to reflect your new requirement

awk '{for (i=1; i<=NF; i++) printf("%d %d\n", $i, $(i+1))}' filename
# ----------------^ 

This takes advantage of the fact that awk treats uninitialized values (here $(NF+1)) as an empty string (in string context) or zero (in numeric context).

Answer 2

Try doing this in perl

 perl -lane '$c=0; for (@F){ print "$F[$c]\t$F[$c+=1]" if $F[$c+1]}' file.txt

Or decomposed :

perl -lane '
    $c=0;
    for (@F) {
        print "$F[$c]\t$F[$c+=1]"
            if $F[$c+1];
    }
' file.txt

EXPLANATIONS

• lane switchs means : l=newlines ; a=autosplit in @F array ; n=like while (<>) magic diamond operator ; e=basic switch to run a command
• $c=0 assign 0 to a counter
• for (@F) { for each element of the current line
• print "$F[$c]\t$F[$c+=1]" : print array element with indice $c + tab + $c+1
• if $F[$c+1]; : apply last line only if $F[$c+1] is not null

Or using bash (same algorithm), maybe more human readable for beginners :

while read a; do
    arr=( $a )
    for ((i=0; i< ${#arr[@]}; i++)); do
        [[ ${arr[i+1]} ]] && echo "${arr[i]} ${arr[i+1]}"
    done
done < file.txt

Answer 3

Here's a pure bash solution:

while read -a a; do
    for ((i=0;i<${#a[@]}-1;++i)); do
        echo "${a[@]:i:2}"
    done
done < file.txt