Automate a shell script using variables from a txt file

Question

I have a list of servers in a addresses.txt file in the following format

xx.xxx.xx.xx
xx.xxx.xxx.xx
xxx.xx.xx.xx

The ip addresses change everyday and I get a new .txt file. The number of servers might change everyday. Im using a Mac so Im using csshx.

I'm trying to csshx into the servers so I need to create a command like this everyday.

csshx -login username --ssh_args "-i ~/.ssh/sshkey" xx.xxx.xx.xx xx.xxx.xxx.xx xxx.xx.xx.xx.

Is there a way to create a shell script so that I can just run the cssh -login username --ssh_args "-i ~/.ssh/sshkey" part and automate the rest of the line using variables from the addresses.txt file? I was thinking of using a for loop but the command needs to be in 1 line.

haha okay I did not think of that.

anarchy
– anarchy

2020-04-30 23:04:50 +00:00
Commented Apr 30, 2020 at 23:04 — anarchy
– anarchy, Commented Apr 30, 2020 at 23:04

Arkku · Accepted Answer · 2020-04-30 23:29:34Z

2

The traditional way would be with backtick or $() command substitution and cat to output the file:

csshx -login username --ssh_args "-i ~/.ssh/sshkey" `cat addresses.txt`

More modern shells allow you to replace cat with <:

csshx -login username --ssh_args "-i ~/.ssh/sshkey" $(< addresses.txt)

Any whitespace in the file is treated as an argument separator, so the server addresses may be separated either by newlines or by spaces/tabs.

edited Apr 30, 2020 at 23:29

answered Apr 30, 2020 at 23:07

Arkku

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5 Comments

Shawn Over a year ago

Why is $(...) preferred over backticks?

Arkku Over a year ago

re. $( ) being preferred over backticks, in writing scripts I definitely prefer and recommend $( ), but for interactive use where the command substitution is typically simple, I must admit I favour the backticks for being quicker to type.

Jetchisel Over a year ago

Fails if there are spaces tabs in the file, in this case there are none

Arkku Over a year ago

@Jetchisel Yes, any whitespace is treated as a separator, but since the question was about hostnames/addresses, one might even consider this a feature.

user1934428 Over a year ago

@Shawn : You can not nest backticks.

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