append variables from a while loop into a command line option

Question

I have a while loop, where A=1~3

mysql -e "select A from xxx;" while read A; 

do 

whatever

done

The mySQL command will return only numbers, each number in each line. So the while loop here will have A=1, A=2, A=3

I would like to append the integer number in the loop (here is A=1~3) into a command line to run outside the while loop. Any bash way to do this?

parallel --joblog test.log --jobs 2 -k sh ::: 1.sh 2.sh 3.sh

Can you clarify the output from the mysql command (is it always just numbers? Is each on a separate line, or separated by spaces and/or commas, or something else?). Also, it looks like you want ".sh" appended to each one; is that correct? — Gordon Davisson
– Gordon Davisson, Commented Sep 22, 2017 at 3:57
Yes, each number on a separate line from the MySQL command. Also, yes on the .sh appended to each one. I also edit the question! Thanks! @Gordon Davisson — Chubaka
– Chubaka, Commented Sep 22, 2017 at 7:11

Ljm Dullaart · Accepted Answer · 2017-09-22 17:42:41Z

2

You probably want something like this:

mysql -e "select A from xxx;" | while read A; do 
    whatever > standard_out 2>standard_error
    echo "$A.sh"
done | xargs parallel --joblog test.log --jobs 2 -k sh :::

edited Sep 22, 2017 at 17:42

answered Sep 22, 2017 at 10:02

Ljm Dullaart

5,0092 gold badges19 silver badges35 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Gordon Davisson Over a year ago

You can simplify this a bit by replacing the while loop with sed 's/$/.sh/'.

Ljm Dullaart Over a year ago

I simply stated an echo instead of the "whatever", assuming that some other commands might be executed as well. If that is not the case, the sed is indeed the way to go. (added whatever to the loop)

Chubaka Over a year ago

Could you enlighten more details on your solution, @GordonDavisson? Thanks.

Gordon Davisson Over a year ago

@Chubaka If the only thing the loop is doing is appending ".sh" to each line, the sed command I gave will do the same thing. If it's doing more than that (e.g. writing to a file), then it won't work as a replacement for the loop.

Chubaka Over a year ago

@GordonDavisson ah i see. Yes, the while loop does more than appending .sh. This is a simplified case.

Chubaka · Accepted Answer · 2017-09-22 18:17:21Z

0

Thanks for enlightening me. xargs works perfectly here:

Assuming we have A.csv (mimic the mysql command)

We can simply do:

cat A.csv | while read A; do

echo "echo $A" > $A.sh

echo "$A.sh"

done | xargs -I {} parallel --joblog test.log --jobs 2 -k sh ::: {}

The above will print the following output as expected

Here -I {} & {} are the argument list markers:

https://www.cyberciti.biz/faq/linux-unix-bsd-xargs-construct-argument-lists-utility/

answered Sep 22, 2017 at 18:17

Chubaka

3,19511 gold badges46 silver badges69 bronze badges

Collectives™ on Stack Overflow

append variables from a while loop into a command line option

2 Answers 2

5 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related