{"id":3045,"date":"2020-01-07T16:13:40","date_gmt":"2020-01-07T21:13:40","guid":{"rendered":"http:\/\/bluegalaxy.info\/codewalk\/?p=3045"},"modified":"2020-01-07T16:13:42","modified_gmt":"2020-01-07T21:13:42","slug":"how-to-use-the-linux-od-command-octal-dump","status":"publish","type":"post","link":"https:\/\/bluegalaxy.info\/codewalk\/2020\/01\/07\/how-to-use-the-linux-od-command-octal-dump\/","title":{"rendered":"How to use the Linux od command (Octal Dump)"},"content":{"rendered":"

I was in a command terminal “bash” window on my Mac and I tried to run this curl command to get a security token from a web service api:
curl -d \"Username=mywebsite&Password=password\" -X POST https:\/\/dev-warehouseapi.somewebsiteservice.com\/api\/Token<\/code><\/p>\n

However, my curl command failed with the message “curl: no URL specified!”. For example:<\/p>\n\n\n

\"\"<\/figure>\n\n\n\n

My curl command appeared to be perfect, so I decided to investigate whether or not there are any special characters hidden in the URL that aren’t visible. <\/p>\n\n\n\n

One way to do this is to use the Linux od<\/code> command, which stands for “Octal Dump”. This command will output a representation of what each character contains. The complete command looks like this:<\/p>\n\n\n\n

echo 'curl -d \"Username=mywebsite&Password=password\" -X POST\u00a0https:\/\/dev-warehouseapi.somewebsiteservice.com\/api\/Token' | od -c<\/code><\/p>\n\n\n\n

This starts with the echo<\/code> command for outputting the characters to the terminal window. Then I paste the string of my original command, surrounded by single quotes in order to escape the double quotes in my command string. After the command string, I use a pipe symbol |<\/code> which means to pass the output of the previous command as input to the following command. Finally, I use the od<\/code> command with -c<\/code> as an argument. The -c<\/code> argument tells od<\/code> to show the output in character format. <\/p>\n\n\n\n

Here is a screen shot of the complete command along with its output:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The special characters shown boxed in red were the hidden characters that were preventing my curl<\/code> command from working. This revealed what I needed to do to fix the command string. I just need to delete the special character and ensure that there is only a blank space between POST and https in the command string. Running the fixed command string through the od command yields:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Success!
This demonstrates the value in using the Linux od<\/code> command to find special characters that are invisible to the eye. <\/p>\n\n\n\n

For more information about the Linux od<\/code> command and other options this command supports, see:
https:\/\/www.thegeekstuff.com\/2012\/08\/od-command\/<\/a><\/p>\n\n\n\n

For more details about the echo<\/code> command, see:
https:\/\/www.linuxhelp.com\/echo-commands-in-linux-2<\/a><\/p>\n\n\n\n

For more about the pipe |<\/code> command, see:
https:\/\/linuxhint.com\/linux_pipe_command\/<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

I was in a command terminal “bash” window on my Mac and I tried to run this curl command to get a security token from a web service api:curl -d “Username=mywebsite&Password=password” -X POST https:\/\/dev-warehouseapi.somewebsiteservice.com\/api\/Token However, my curl command failed with the message “curl: no URL specified!”. For example: My curl command appeared to be perfect, … Continue reading How to use the Linux od command (Octal Dump)<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[78],"tags":[98,60,217],"class_list":["post-3045","post","type-post","status-publish","format-standard","hentry","category-technologies-and-tools","tag-echo","tag-linux","tag-od"],"_links":{"self":[{"href":"https:\/\/bluegalaxy.info\/codewalk\/wp-json\/wp\/v2\/posts\/3045","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bluegalaxy.info\/codewalk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bluegalaxy.info\/codewalk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bluegalaxy.info\/codewalk\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bluegalaxy.info\/codewalk\/wp-json\/wp\/v2\/comments?post=3045"}],"version-history":[{"count":6,"href":"https:\/\/bluegalaxy.info\/codewalk\/wp-json\/wp\/v2\/posts\/3045\/revisions"}],"predecessor-version":[{"id":3055,"href":"https:\/\/bluegalaxy.info\/codewalk\/wp-json\/wp\/v2\/posts\/3045\/revisions\/3055"}],"wp:attachment":[{"href":"https:\/\/bluegalaxy.info\/codewalk\/wp-json\/wp\/v2\/media?parent=3045"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bluegalaxy.info\/codewalk\/wp-json\/wp\/v2\/categories?post=3045"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bluegalaxy.info\/codewalk\/wp-json\/wp\/v2\/tags?post=3045"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}