DIE SH DIE DIE DIE

"/bin/sh: It works, but it's far from not being a nightmare"

https://skarnet.org/software/execline/dieshdiedie.html

#C #Sh #shell #csh #tcsh #bash #dash #zsh #posix #execline

@ska @tromo

So, after I met problems with iwlwifi driver and my attempts to aggregate both em0 and wlan0 interfaces to the one lagg0 interface (https://mastodon.bsd.cafe/@evgandr/115985853500057386) — looks like I found a much (MUCH!) simpler solution 

I wanted to automatically switch between wired and wireless networks when I plug-in (or disconnect) my Ethernet cable. First, because I was a newbie in the FreeBSD world, I tried to search for some kind of NetworkManager. Thankfully, I didn't find any NetworkManager clone ported to the FreeBSD. I found some tries to port NetworkManager from Linux to FreeBSD but all of them are failed (not surprised, lol).

Then, I finally started to read documentation  . In the section about advanced networking I read about aggregation interfaces. And somehow I managed to aggregate both of em0 and wlan0 to the one lagg0 interface and it works well.

But, looks like (see https://mstdn.social/@erikarn/115986265106931691) it is not the way how the lagg interfaces should work. It is not intended to use wireless interfaces in the aggregate interfaces — so my tricky setup stopped working in the FreeBSD 15.0.

BUT, since we have a beautiful devd daemon, which listens for various system events and able to execute actions when event is happened — I just wrote 23 lines of shell script to learn my laptop how to switch between interfaces when the Ethernet cable (dis)connects, lol. Solution is very simple:

First, we already have /etc/devd/dhclient.conf, which starts dhclient when some interface appeared in the system. I modified it, so it calls the sPeCiAL script, each time when em0, or wlan0, or ue0 interface appeared in the system, or when em0 is disappeared:

notify 0 {
match "system" "IFNET";
match "type" "LINK_UP";
media-type "ethernet";
action "/root/bin/unfuck_network.tcsh $subsystem ifup";
};

notify 0 {
match "system" "IFNET";
match "type" "LINK_DOWN";
media-type "ethernet";
action "/root/bin/unfuck_network.tcsh $subsystem ifdown";
};

notify 0 {
match "system" "IFNET";
match "type" "LINK_UP";
media-type "802.11";
action "/root/bin/unfuck_network.tcsh $subsystem";
};

notify 0 {
match "system" "ETHERNET";
match "type" "IFATTACH";
match "subsystem" "ue0";
action "/root/bin/unfuck_network.tcsh ue0";
};

Then, the main magic happens in the /root/bin/unfuck_network.tcsh:
— When Ethernet cable is connected — it destroys the wlan0 interface and starts dhclient for em0 to talk with DHCP server.
— When Ethernet cable is disconnected — it makes all to remove route using em0 from routing table (removes em0 interface completely, flush routing table, etc — somehow em0 still stays in the routing table if interface is not destroyed; btw system will create it anyway later, in some point) and recreates the wlan0 interface.
— When wlan0 device is created — it starts dhclient for it.

Script contents (for tcsh):
#!/bin/tcsh

switch ( $1 )
case "em0":
if ( $2 == "ifup" ) then
service netif quietstop wlan0
service dhclient quietstart em0
else if ( $2 == "ifdown" ) then
service dhclient quietstop em0
ifconfig em0 delete
route flush
service routing restart
service netif quietstart wlan0
endif
breaksw;
case "wlan0":
service dhclient quietstart wlan0
breaksw;
case "ue0":
service dhclient quietstart ue0
breaksw;
endsw

#FreeBSD #FreeBSD150RELEASE #wifi #tcsh #devd #iwm

Preparing an engineering-focused presentation entitled "The Zen of Shell Scripting" for an internal talk at work. Question for seasoned Shell programmers: What would you have liked to know when you first started out? Interested in both big ideas and sharp edges that come with Shell scripting.

#shell #unix #linux #posix #bash #zsh #tcsh #ksh #fish

#Lesson of the day: I waste time searching for a solution #online, then ask #AI, which gives me “wonderful” but completely wrong results. In the end, I read the official #documentation and solve it in a few seconds:

1. https://man.freebsd.org/tcsh/1 > 2. Ctrl-f > 3. type "redirect" > 4. "The shell cannot presently redirect diagnostic output without also redirecting standard output, but `(command > output-file) >& error-file' is often an acceptable workaround. ..."

#Documentation #UNIX #FreeBSD #Shell #scripting #terminal #tcsh #fixing

Serious question for CLI users.

Do you think it’s insane to use an interactive shell and to code your scripts for a totally different shell?

#shell #unix #linux #bash #sh #fish #tcsh #csh #cli

If I've never seen the codebase, which #Linux shell has the easiest code to read and understand? Specifically I want to isolate the code for *parsing* the command line syntax.

All #POSIX-compliant (or close enough) shells welcome! I probably don't know them all but off the top of my head:

#bash
#dash
#fish (sorry for the spam, marine life enthusiasts)
#zsh
#ksh
#tcsh & #csh I think?

#shell #shells #foss #code #commandline

#Poll: Curious about people's attitudes towards shell scripting.

Two part question:

#Unix #UnixShell #ShellScript #ShellScripting #POSIX #PosixShell #sh #bash #zsh #csh #tcsh #ksh #pdksh #oksh #mksh