Bash script pass in variable with new lines

Question

I have a script which runs a mysql query on multiple database. i have it logging the query which was run to a file. When i pass in the query it contains new lines, but in the log file its is all on one line. Multi line queries are easier to read.

e.g:

$ sh run_query.sh 'CREATE TABLE`table` ( 
`id` int(10) unsigned NOT NULL AUTO_INCREMENT, 
`field1` int(10) unsigned NOT NULL, 
`field2` int(10) unsigned NOT NULL, 
PRIMARY KEY (`id`), 
 ENGINE=InnoDB;'

Is it possible for bash to keep the new lines in a passed variable?

The string itself is fine. The question is, how are you using (i.e., quoting) the parameter inside run_query.sh? — chepner
– chepner, Commented Sep 16, 2015 at 11:06
I am simply echoing into a log file. but strange that a simple echo strips out the new lines. Is there a parameter to echo which will keep them? — Wardy277
– Wardy277, Commented Sep 16, 2015 at 16:19

chepner · Accepted Answer · 2015-09-16 16:30:40Z

1

In your comment, you mention using this code:

echo $sql >> logfile

However, this causes the shell to treat any newline character present in the value of $sql as whitespace to separate the string into multiple arguments for echo. You need to quote the expansion:

echo "$sql" >> logfile

answered Sep 16, 2015 at 16:30

chepner

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Comments

anubhava · Accepted Answer · 2015-09-16 10:03:29Z

0

You can store multiline string in a variable first like this:

IFS= read -rd '' sql <<'EOF'
CREATE TABLE`table` ( 
`id` int(10) unsigned NOT NULL AUTO_INCREMENT, 
`field1` int(10) unsigned NOT NULL, 
`field2` int(10) unsigned NOT NULL, 
PRIMARY KEY (`id`), 
ENGINE=InnoDB;
EOF

Then pass it as:

sh run_query.sh "$sql"

answered Sep 16, 2015 at 10:03

anubhava

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2 Comments

chepner Over a year ago

There's no need to go through such contortions to set the value of sql. Newlines can be embedded in quotes as shown in the question.

anubhava Over a year ago

Of course that may work but you understand very well a SQL can have single and double quotes and then this quoted string won't work.

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