Cyufjy

I have two variables which contain multiline information and i want to column them.

varA returns

Aug 01
Aug 04
Aug 16
Aug 26

and varB returns

04:25
07:28
03:39
10:06

if i print both variables, it returns

Aug01
Aug04
Aug16
Aug26
04:25
07:28
03:39
10:06

What i want to do is the following:

Aug01 04:25
Aug04 07:28
Aug16 03:39
Aug26 10:06

I'm new in Linux and i would appreciate some advice, thanks.

Meet paste, part of the preinstalled GNU core utilities:

$ paste <(printf "%s" "$varA") <(printf "%s" "$varB")
Aug 01 04:25
Aug 04 07:28
Aug 16 03:39
Aug 26 10:06

paste takes files and not variables as input, so I used bash Process Substitution and just printed the variable content with printf. The default delimiter between columns is TAB, you can change that with the -d option, e.g. paste -d" " for a single space character. To learn more about paste have a look at the online manual or run info '(coreutils) paste invocation'.

If you just want to simply display the text variables side by side, @dessert has the most simple (best?) solution using print. However if you want to be able to manipulate each piece individually, you could easily convert the vars to arrays instead, and loop through that.

#!/bin/bash

# declare the multi-line variables
var1="1
2
3
4"
var2="a
b
c
d"

# backup internal field separator to be safe
IFSave=$IFS

# set IFS to newline so vars will use newline to split into array
IFS=$'n'

# split variables into array
foo=($var1)
bar=($var2)

#restore IFS to original value to be safe
IFS=$IFSave

# loop array foo, and cross reference key in array bar
for i in "$!foo[@]"; do 
 printf "$foo[$i] : $bar[$i]n"
done

# you can allso now print single corresponding lines:
line=3

let id=$line-1 # arrays start at 0, so need to remove one

printf "nPrinting line number $linen"
printf "$foo[$id] : $bar[$id]n"

If you wanted to avoid external utilities and do it natively in the shell, you could use read with separate file descriptors / here strings for each variable:

while IFS= read -r -u3 a && read -r -u4 b; do 
 printf '%st%sn' "$a" "$b"
done 3<<<"$varA" 4<<<"$varB"
Aug 01 04:25
Aug 04 07:28
Aug 16 03:39
Aug 26 10:06

Although it's often considered bad practice to use the shell for text processing, it might be excused in the case that you already have the data in shell variables.

You can do this with the POSIX tool pr:

varA='Aug 01
Aug 04
Aug 16
Aug 26'
varB='04:25
07:28
03:39
10:06'
pr -2 -t <<eof
$varA
$varB
eof

Result:

Aug 01 04:25
Aug 04 07:28
Aug 16 03:39
Aug 26 10:06

Or for single tab:

pr -2 -t -s

Or for single space:

pr -2 -t -s' '

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/pr.html

Or with column from the util-linux package:

column -c 20 <<eof
$varA
$varB
eof

paste used with column provides clean output. For convenience of most users I'll use an example of directories already on their system.

$ cd /sys/devices/system/cpu/cpu0/cpufreq

$ ls
affected_cpus energy_performance_preference scaling_governor
cpuinfo_max_freq related_cpus scaling_max_freq
cpuinfo_min_freq scaling_available_governors scaling_min_freq
cpuinfo_transition_latency scaling_cur_freq scaling_setspeed
energy_performance_available_preferences scaling_driver

$ cat *
0
3500000
800000
4294967295
default performance balance_performance balance_power power 
balance_performance
0
performance powersave
875982
intel_pstate
powersave
3500000
800000
<unsupported>

$ paste <(ls *) <(cat *) | column -s $'t' -t
affected_cpus 0
cpuinfo_max_freq 3500000
cpuinfo_min_freq 800000
cpuinfo_transition_latency 4294967295
energy_performance_available_preferences default performance balance_performance balance_power power 
energy_performance_preference balance_performance
related_cpus 0
scaling_available_governors performance powersave
scaling_cur_freq 1079503
scaling_driver intel_pstate
scaling_governor powersave
scaling_max_freq 3500000
scaling_min_freq 800000
scaling_setspeed <unsupported>

Without the column command, the fields in the second column are unaligned, making it more difficult to read.

$ paste <(ls *) <(cat *)
affected_cpus 0
cpuinfo_max_freq 3500000
cpuinfo_min_freq 800000
cpuinfo_transition_latency 4294967295
energy_performance_available_preferences default performance balance_performance balance_power power 
energy_performance_preference balance_performance
related_cpus 0
scaling_available_governors performance powersave
scaling_cur_freq 1943068
scaling_driver intel_pstate
scaling_governor powersave
scaling_max_freq 3500000
scaling_min_freq 800000
scaling_setspeed <unsupported>

For more column command examples see this article: Viewing Linux output in columns

If the column command is not already installed use:

sudo apt update
sudo apt install util-linux