Question

This is really self explanatory. I’m working in a bash shell and I’m really new to shell scripting. I’ve found a lot of information about using tr and sed but all the examples I have found so far are removing delimiters and new lines. I really want to do the opposite of that. I want to be able to separate based on a blank space. I have a string like “abcd efgh” and I need it to be “abcd” “efgh” (all without quotes, just to show groupings).

I’m sure this is much simpler than I’m making it, but I’m very confused.

Updated Question:

I have a column of PIDs that I have put into an array, but each element of the array has both the pids in the column.

Column:

1234
5678

when I print out the entire array, all the different columns have been added so I have all the values, but when I print out a single element of my array I get something like:

1234 5678

which is not what I want.
I need to have an element for 1234 and a separate one for 5678.

This is my code so far:

!/bin/bash
echo "Enter the File Name"
read ips

index=0
IFS=' '
while read myaddr myname; do
    myips[$index]="$myaddr"
    names[$index]="$myname"
    index=$(($index+1))
done < $ips

echo "my IPs are: ${myips[*]}"
echo "the corresponding names are: ${names[*]}"
echo "Total IPs in the file: ${index}"

ind=0
for i in "$myips[@]}"
do
    echo $i
    pids=( $(jps | awk '{print $1}') )

    for pid in "${pids[@]}"; do
        echo $pid
    done

    echo "my PIDs are: ${pids}"

    for j in "${pids[@]}"
    do
        mypids[$ind]="$j"
        ind=$(($ind+1))
    done
done
echo "${mypids[*]}"
echo "The 3rd PID is: ${mypids[2]}"

SAMPLE OUTPUT:

Total IPs in the file: 6

xxx.xxx.xxx.xxx
5504
1268
1
xxx.xxx.xxx.xxx
5504
4352
1

xxx.xxx.xxx.xxx
5504
4340
1

5504
1268 5504
4352 5504
4340

The 3rd pid is: 5504
4340

I need each pid to be separate, so that each element of the array, is a single pid. So for instance, the line “The 3rd pid is: ” needs to look something like

The 3rd pid is: 5504

and the 4th element would be 4340

Answer 1

Try cut:

$ echo "abcd efgh" | cut -d" " -f1
abcd

$ echo "abcd efgh" | cut -d" " -f2
efgh

Alternatively, if at some point you want to do something more complex, do look into awk as well:

$ echo "abcd efgh" | awk '{print $1}'
abcd

$ echo "abcd efgh" | awk '{print $2}'
efgh

---

To address your updated question:

I have a column of PIDs that I have put into an array, but each element of the array has both the pids in the column.

If you want to load a column of data into an array, you could do something like this:

$ pgrep sshd  # example command. Get pid of all sshd processes
795
32046
32225

$ A=(`pgrep sshd`) # store output of command in array A

$ echo ${A[0]}  # print first value
795

$ echo ${A[1]}  # print second value
32046

---

To address the example code you posted, the reason for your problem is that you’ve change $IFS to a space (IFS=' ') which means that your columns which are separated by newlines are no longer being split.

Consider this example:

$ A=(`pgrep sshd`)
$ echo ${A[0]}  # works as expected
795

$ IFS=' '       # change IFS to space only
$ A=(`pgrep sshd`)  
$ echo ${A[0]}  # newlines no longer used as separator
795
32046
32225

To avoid this problem, a common approach is to always backup the original IFS and replace it once you’ve done using the updated value. E.g.

# backup original IFS
OLDIFS=$IFS

IFS=' '
# .. do stuff ...

# restore after use
IFS=$OLDIFS