Let's start off with the response to this question (Why is a multi-line output saved as one line in a variable?): It's not!
As I'm currently improving the monitoring plugin check_couchdb_replication, I came across a little problem.
I wanted to check the number of lines of a curl output. By simply using the curl command directly, I got 29 lines in return:
$ curl -q -s localhost:5984/_scheduler/docs/_replicator -u admin:secret | wc -l
But when I saved the command's output in a variable, the whole output seems to have merged into one line:
$ output=$(curl http://localhost:5984/_scheduler/docs/_replicator -u admin:secret)
$ echo $output | wc -l
I came across an article on StackOverflow where the solution was presented. Which by the way is surprisingly easy:
$ echo "$output" | wc -l
By simply putting the variable into double-quotes, the correct number of lines is shown again. But why is that? In the same article linked above, the explanation from Jonathan Leffler is really good:
the difference is that (1) the double-quoted version of the variable (echo "$VARIABLE") preserves internal spacing of the value exactly as it is represented in the variable — newlines, tabs, multiple blanks and all — whereas (2) the unquoted version (echo $VARIABLE) replaces each sequence of one or more blanks, tabs and newlines with a single space. Thus (1) preserves the shape of the input variable, whereas (2) creates a potentially very long single line of output
Quite crazy that after more than 10 years of bashing I only came across this today.
Will from wrote on Jul 21st, 2021:
Thank you so much!
Tomica from wrote on Jan 29th, 2021:
Wow, that really is easy :)
Sebastian from Fiji wrote on Nov 23rd, 2020:
Anders from wrote on Sep 24th, 2020:
And by sharing this little info, you reached top google hit on the subject. Leffler explained it very well.
Marcelo from United States wrote on Jan 15th, 2020:
THANK YOU! :)
hshhhhh from wrote on Sep 4th, 2019:
oh man, thank you.
I hate bash so much because it should be renamed to "WBSH" - "Weird Behaviou SHell"
AWS Android Ansible Apache Apple Atlassian BSD Backup Bash Bluecoat CMS Chef Cloud Coding Consul Containers CouchDB DB DNS Database Databases Docker ELK Elasticsearch Filebeat FreeBSD Galera GlusterFS Grafana Graphics HAProxy HTML Hacks Hardware Icinga Icingaweb Icingaweb2 Influx Internet Java KVM Kibana Kodi Kubernetes LXC Linux Logstash Mac Macintosh Mail MariaDB Minio MongoDB Monitoring Multimedia MySQL NFS Nagios Network Nginx OSSEC OTRS Office PGSQL PHP Perl Personal PostgreSQL Postgres PowerDNS Proxmox Proxy Python Rancher Rant Redis Roundcube SSL Samba Seafile Security Shell SmartOS Solaris Surveillance Systemd TLS Tomcat Ubuntu Unix VMWare VMware Varnish Virtualization Windows Wireless Wordpress Wyse ZFS Zoneminder