{"id":122,"date":"2020-05-11T23:36:40","date_gmt":"2020-05-11T22:36:40","guid":{"rendered":"https:\/\/blog.thomarite.uk\/?p=122"},"modified":"2020-05-11T23:43:19","modified_gmt":"2020-05-11T22:43:19","slug":"bash-shell-quoting","status":"publish","type":"post","link":"https:\/\/blog.thomarite.uk\/index.php\/2020\/05\/11\/bash-shell-quoting\/","title":{"rendered":"Bash: shell quoting"},"content":{"rendered":"\n

Another issue I had during the weekend that took me hours. Thanks that I have been reading a bit this book<\/a> (1.6) and had some clues.<\/p>\n\n\n\n

I was trying to test a repo<\/a> to start an Arista<\/a> lab using docker and I assumed that everything should work if I followed the instructions. My problem was the script trying to push some basic config to the switches.<\/p>\n\n\n\n

This is was the initial function:<\/p>\n\n\n\n

#!\/usr\/bin\/env bash\n...\nfunction fast_cli() {\n  params=\"${*:2}\"\n  commands=\"${params\/\/;\/\\\\\\n}\"\n  docker exec \"${1}\" bash -c \"echo -e ${commands} | FastCli -p15 -e\n}\n...<\/pre>\n\n\n\n
If you type that command in a bash shell directly is something like this:<\/p>\n\n\n\n
$ docker exec DOCKER_ID bash -c 'echo -e \"configure\\n hostname sp01\\n end\\n write\\n\" | FastCli -p15 -e'<\/pre>\n\n\n\n
As you can see that differs with what we have inside the bash script. So from the bash script we need to put between ‘ the parameter for -c but inside the parameter we need to use “. So I had to make the change below:<\/p>\n\n\n\n
-  docker exec \"${1}\" bash -c \"echo -e ${commands} | FastCli -p15 -e\"\n+  # need to update this command as the quoting doesnt work in my bash\n+  docker exec \"${1}\" bash -c 'echo -e '\"'${commands}'\"' | FastCli -p15 -e'\n<\/pre>\n\n\n\n
The books says Enclose a string in single quotes ‘ unless it contains elements that you want the shell to interpolate<\/em>. So let’s divide the solution in parts so can be easier to digest (and remember for me in the future because this will bit me again for sure)<\/p>\n\n\n\n