Quick bash tips

April 05, 2016 | 2 Minute Read

Escape a frozen SSH session

Quite often, I’m working on a project and running commands on the remote server via SSH. Also quite often, I’ll step away from the keyboard long enough or execute an ls in a folder with a stale NFS mount and my SSH session will freeze. My usual solution to get myself out of this situation is to kill my whole terminal and start over.

What I learned today, after searching for all of 2 minutes to find a solution to my recurring problem, is that there a sequence of key you can type to exit the SSH session: enter ~ ..

You need to send the ssh escape sequence, which by default is ~ at the beginning of a line (in other words, preceded by a newline, or enter). Then send the disconnect character, which is .. – http://unix.stackexchange.com/a/78272

As was pointed out by @xerkus on twitter, I just never bothered to read the man page for SSH, especially the section on the escape character:

-e escape_char Sets the escape character for sessions with a pty (default: ‘~’). The escape character is only recognized at the beginning of a line. The escape character followed by a dot (‘.’) closes the connection; followed by control-Z suspends the connection; and followed by itself sends the escape character once. Setting the character to “none” disables any escapes and makes the session fully transparent.

Sequentially call a list of URLs

This afternoon, one of my colleagues had a list of 200+ URLs to call in a sequence. His list was an HTML file with 200 links that he planned to click one by one. A quick Google search and 2 minutes of reading, we had a one-line solution.

First create a file with the plaintext list, then the URLs need to be between quotes…

awk '{ print "\""$0"\""}' urls.txt > quoted-urls.txt

Then we can use curl to call the list line by line…

xargs curl -I < quoted-urls.txt

This command will call the URLs (one per line) in quoted-urls.txt and display the response headers for each. We had to tweak it a little bit to send the Cookie header, because the URLs were in the admin section of the website.

xargs curl -H 'Cookie: session=9ao4g0ci2h8eiovlknspv63ku4;' -I < quoted-urls.txt

By the way, if you found a typo, please fork and edit this post. Thank you so much!