Executing a command via shell script.

bsaidus · May 31, 2023

Hello,
I'm new to shell (.sh) scripting, so I lean slowly

.
I have this command

Code:

 $ dmesg | grep "Ethernet address:" | awk '{ print $1 }' | sed s/://

This command retreive the name if ethernet interface from dmesg kernel journal, and works well when executed from the commande line prompt.
But error is given : not fount when trying to use it in a shell script
Here is the code of script

Code:

#!/bin/sh

#
# Get interface name & replace it.
#
# Get kernel if

Bsd_dmesg="/sbin/dmesg"
Bsd_grep="/usr/bin/grep"
Bsd_sed="/usr/bin/sed"
Bsd_awk="/usr/bin/awk"

# dmesg | grep \"Ethernet address:\" | awk '{ print $1 }' | sed s/://" 
C_ifkern_cmd="${Bsd_dmesg}|${Bsd_grep} \"Ethernet address:\"| ${Bsd_awk} '{ print \$1 }' | ${Bsd_sed} s/://"

  # execute command;
  echo "${C_ifkern_cmd}"
 
  ifnet=$("${C_ifkern_cmd}")
 
  echo "${ifnet}"

exit 0

So please, tel me where is the problem.
The output is

Code:

./ucgetif: /sbin/dmesg|/usr/bin/grep "Ethernet address:"| /usr/bin/awk '{ print $1 }' | /usr/bin/sed s/://: not found

YYY__ · May 31, 2023

dmesg | grep \"Ethernet address:\" | awk '{ print $1 }' | sed s/://"
The last quotes?

aragats · May 31, 2023

You don't need so long chain of commands, here is a simpler way:

Code:

dmesg | sed -n 's/^\(.*\):\ Ethernet\ address.*/\1/p'

cracauer@ · May 31, 2023

You need

Code:

ifnet=$(${C_ifkern_cmd}) # without quotes

Also, you should really grep on /var/run/dmesg,boot instead of the live kernel buffer. The latter has the problem that new messages at runtime will over time swap out the messages you want. There is limited space in there.

Why do you feel you need to hardcode the paths?

The grep can be replaced with an AWK statement

Code:

awk '/grepterm/ {print $1}'

In general, as a beginner you should try not to get into the quoting messes resulting from keeping commands in variables. Have you considered using -x?

SirDice · May 31, 2023

If you just need a list of interfaces; ifconfig -l. No need to grep through system logs.

Code:

     The -l flag may be used to list all available interfaces on the system,
     with no other additional information.  If an address_family is specified,
     only interfaces of that type will be listed.  -l “ether” will list only
     Ethernet adapters, excluding the loopback interface.  Use of this flag is
     mutually exclusive with all other flags and commands, except for -d (only
     list interfaces that are down) and -u (only list interfaces that are up).

ifconfig(8)

bsaidus · May 31, 2023

Thanks you freinds for your answers, I'll try to do my best and give you feedback.

SirDice · May 31, 2023

Don't worry too much about the 'correctness', just have fun and try lots of things. Some learn quickly, some a little slower. But the only way to learn how to do it properly is by actually starting. Everybody's first scripts sucked, my first scripts certainly did

bsaidus · Jun 1, 2023

Hello.
Here is a working script.

Bash:

#!/bin/sh
#
# Get interface name & replace it.
#
Bsd_dmesg="/sbin/dmesg"
Bsd_grep="/usr/bin/grep"
Bsd_sed="/usr/bin/sed"
Bsd_awk="/usr/bin/awk"
Bsd_cat="/bin/cat"
Bsd_msgd="/var/run/dmesg.boot"

#(works ;) ) eth_addresses=$(cat /var/run/dmesg.boot | sed -n 's/^\(.*\):\ Ethernet\ address.*/\1/p')
#(works ;) ) eth_addresses=$(${Bsd_cat} ${Bsd_msgd} | ${Bsd_sed} -n 's/^\(.*\):\ Ethernet\ address.*/\1/p')
#(works ;) ) eth_addresses=$(${Bsd_dmesg} | ${Bsd_sed} -n 's/^\(.*\):\ Ethernet\ address.*/\1/p')

eth_ifs=$(${Bsd_dmesg} | ${Bsd_sed} -n 's/^\(.*\):\ Ethernet\ address.*/\1/p')
rep_pattern="XXXX"
${Bsd_sed} -i '' -e "s/$rep_pattern/$eth_ifs/g" /etc/rc.conf
exit 0

Thank you.

SirDice · Jun 1, 2023

bsaidus said:
Code:

${Bsd_sed} -i '' -e "s/$rep_pattern/$eth_ifs/g" /etc/rc.conf

Instead of using sed(1) on rc.conf you can use sysrc(8) to get/set/change options. Less error prone.

bsaidus · Jun 1, 2023

In my case, I do not know it will feel my needs,
I explain.
I have to work an OS image (.img), and after burning it into SDCard or USB Stick and after kernel messages when starting, I must execute this code ( code above) to replace 'XXXX' in the /etc/rc.conf with the interface name.
In my
`/etc/rc.conf `
I added theses entries.

ifconfig_XXXX_name="genet0"
ifconfig_genet0="inet 192.168.1.177/24"

after executing, the XXXX will be replaced by by the interface name without human intervention.

I wonder if there a way to know interfaces names & there characteristics like, Vendor, Type, MAC address without needing to dump dmesg.boot.?
The C code or shell, ... are welcome.

(PS: I must know all these details in boot time after kernel messages ).

Thanks

SirDice · Jun 1, 2023

Tip, you can use ifconfig_DEFAULT="....". That will always use the first detected ethernet card. Which is usually fine for most generic servers or embedded devices with only one ethernet adapter.

If you need to use a specific interface (for firewall rules for example), you could do ifconfig_DEFAULT_name="eth0". Then base everything on the eth0 interface name. This little 'trick' would work fine for systems that only have one ethernet connection. No need to figure out if it's ng0, or em0, or igb0, it will automagically pick the first interface.

bsaidus · Jun 1, 2023

Thanks all for your help.
You're the best.

bsaidus · Jun 1, 2023

Strange,

# the default interface in my system is "vtnet0" I use FreeBSD 13.2-RPI-aarch64 ( I use QEMU)
ifconfig_DEFAULT_name="genet0"
ifconfig_genet0="inet 192.168.1.177/24"

after rebooting, It stays vtnet0 and the name do not change.
May I missing something ?

T-Daemon · Jun 1, 2023

bsaidus said:
Rich (BB code):

ifconfig_DEFAULT_name="genet0"

Only ifconfig_DEFAULT is a valid variable, ifconfig_DEFAULT_name is not.

SirDice · Jun 2, 2023

Oh, you're right. I could have sworn I had this working at some point in time.

bsaidus · Jun 2, 2023

Hello.
After many tries, I think about writing and /rc.d/* script that must be executed before network stack start, that changes the pattern XXXX from /etc/rc.conf with the detected kernel device name.

The question is : CAN I DO THIS ? and HOW. (Pointing me to a sample exemple is welcome.)
Thank you.

W.hâ/t · Jun 2, 2023

if I understand correctly, its main use case is with install scripts using ifconfig_DEFAULT="DHCP". If a static ip is set, lo0 will be set with this ip too.

Here maybe a little bit faster solution using pciconf(8)

Code:

# pciconf -lv | grep -B4 ethernet | head -n 1 | cut -c -4
bge0

bsaidus said:
The question is : CAN I DO THIS ? and HOW. (Pointing me to a sample exemple is welcome.)

Have a look at rc(8) and rc.subr(8).
There are plenty examples in /etc/rc.d/* and /usr/local/etc/rc.d/* or online.

T-Daemon · Jun 2, 2023

I thought about that earlier how that can be accomplished. Changing the network interface name would be a onetime action. Running the script only once can be done with the firstboot sentinel keyword. For example sysutils/firstboot-pkgs is designed to install packages after first booting a newly installed system.

The relevant part of the script is

Code:

#!/bin/sh

# KEYWORD: firstboot

Also a empty /firstboot file must be present on the new system.

rc.conf(5)

Code:

    firstboot_sentinel
                 (str) This variable specifies the full path to a “first boot”
                 sentinel file.  If a file exists with this path, rc.d scripts
                 with the “firstboot” keyword will be run on startup and the
                 sentinel file will be deleted after the boot process
                 completes.  The sentinel file must be located on a writable
                 file system which is mounted no later than early_late_divider
                 to function properly.  The default is /firstboot.

And second, the script needs to be run before the network configuration:

Code:

# BEFORE: netif

bsaidus · Jun 2, 2023

W.hâ/t , what I want to do is :

installing the FreeBSD OS ( My version ) on SDCard, USBStick.
After kernel loading & devices driver detection I want that the first ethernet device renamed without human intervention into the system.
So, I created a script above ( script ) to do this.
I've tried to place it into /etc/rc but the network interface starts before it, if I call it from the begin of /etc/rc, the filesystem is read only.
I thought to create and rc.d/ script to do this task before starting a network stack

I do not know if it is a good solution and I do not see other solution

T-Daemon · Jun 2, 2023

Eric A. Borisch has a similar rc.d script written, ethname, for re-naming devices based on their MAC address.

ethname/ethname at master · eborisch/ethname

FreeBSD rc.d script to map ethernet device names by MAC address. - ethname/ethname at master · eborisch/ethname

github.com

T-Daemon · Jun 2, 2023

bsaidus said:
4. I've tried to place it into /etc/rc but the network interface starts before it

Use in the rc.d script the BEFORE: netif keyword.

T-Daemon · Jun 2, 2023

bsaidus said:
So, I created a script above ( script ) to do this.

I've tried to place it into /etc/rc

The rc(8) script needs to have a specific structure, see examples in the manual. Your code can be placed inside the rc.d script, or saved in a location read by the PATH variable and pointed to it.

Non-system rc.d scripts should be placed under directory /usr/local/etc/rc.d.

W.hâ/t · Jun 2, 2023

bsaidus said:
W.hâ/t , what I want to do is :

installing the FreeBSD OS ( My version ) on SDCard, USBStick.

After kernel loading & devices driver detection I want that the first ethernet device renamed without human intervention into the system.

So, I created a script above ( script ) to do this.

I've tried to place it into /etc/rc but the network interface starts before it, if I call it from the begin of /etc/rc, the filesystem is read only.

I thought to create and rc.d/ script to do this task before starting a network stack

I do not know if it is a good solution and I do not see other solution

T-Daemon mentions the keywords you need to use in your rc script. You can use your method or mine or an other, it doesn't matter, as long as you use the correct keywords. Here firstboot doesn't suit you in this case.

Now with what you're trying to accomplish, I would say setting ifconfig_DEFAULT="DHCP" should be enough. Altough I surely won't stop you from messing arrround with stuff.
A quick though, what about wlan interfaces?

bsaidus · Jun 2, 2023

Feedback.
I created an rc file and put it in :

# operations
$ /usr/local/etc/rc.d/ucgetif
$ chmod +x /usr/local/etc/rc.d/ucgetif

listning of the file /usr/local/etc/rc.d/ucgetif

Bash:

#!/bin/sh

# PROVIDE: ucgetif
# REQUIRE: FILESYSTEMS
# BEFORE: hostname

. /etc/rc.subr

name="ucgetif"
rcvar="ucgetif_enable"

start_cmd="${name}_start"

Bsd_dmesg="/sbin/dmesg"
Bsd_grep="/usr/bin/grep"
Bsd_sed="/usr/bin/sed"
Bsd_awk="/usr/bin/awk"
Bsd_cat="/bin/cat"
Bsd_msgd="/var/run/dmesg.boot"

ucgetif_start() {
      eth_patern="XXXX"
      eth_X=$(${Bsd_cat} /etc/rc.conf | ${Bsd_grep} $eth_patern)
      if [ -n $eth_X ]; then
        eth_ifs=$(${Bsd_dmesg} | ${Bsd_sed} -n 's/^\(.*\):\ Ethernet\ address:.*/\1/p')
        $Bsd_sed -i '' -e "s/$eth_patern/$eth_ifs/g" /etc/rc.conf
      fi 
}

run_rc_command "$1"

Modification done on /etc/rc.conf

After reboot, here is the log :

 

ELF ldconfig path: /lib /usr/lib /usr/lib/compat /usr/local/lib /usr/local/lib/compat/pkg /usr/local/lib/compat/pkg /usr/local/lib/perl5/5.32/mach/CORE

Setting up harvesting: [UMA],[FS_ATIME],SWI,INTERRUPT,NET_NG,[NET_ETHER],NET_TUN,MOUSE,KEYBOARD,ATTACH,CACHED

Feeding entropy: .

Setting hostname: uc-rpi.uccen.net.

ifconfig: SIOCIFCREATE2 (wlan): Invalid argument

[B]vtnet0: changing name to 'genet0'

genet0[/B]

lo0: link state changed to UP

genet0: link state changed to UP

Starting Network: lo0 genet0.

lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384

        options=680003<RXCSUM,TXCSUM,LINKSTATE,RXCSUM_IPV6,TXCSUM_IPV6>

        inet6 ::1 prefixlen 128

        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x2

        inet 127.0.0.1 netmask 0xff000000

        groups: lo

        nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>

genet0: flags=8863<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500

        options=80028<VLAN_MTU,JUMBO_MTU,LINKSTATE>

        ether 52:54:00:12:34:56

        media: Ethernet autoselect (10Gbase-T <full-duplex>)

        status: active

        nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>

Starting devd.

add host 127.0.0.1: gateway lo0 fib 0: route already in table

add host ::1: gateway lo0 fib 0: route already in table

add net fe80::: gateway ::1

add net ff02::: gateway ::1

add net ::ffff:0.0.0.0: gateway ::1

add net ::0.0.0.0: gateway ::1

Updating motd:.

Clearing /tmp (X related).

Updating /var/run/os-release done.

Conclusion ;
It change effectivelly the interface name ( and modify the XXXX in /etc.rc.conf) , but It do not apply IP address until restart.
Is there any way or I'm messing something.
Thanks

PS: Look at the image

T-Daemon · Jun 2, 2023

bsaidus said:
It change effectivelly the interface name ( and modify the XXXX in /etc.rc.conf) , but It do not apply IP address until restart.
Is there any way or I'm messing something.

You are missing the netif script. /etc/rc.d/netif is automaticaly run for network interface setup. ucgetif must run before.

Other, without firstboot sentinel ucgetif will be run every time the system boots up.

Suggestion:

Code:

#!/bin/sh

# PROVIDE: ucgetif
# REQUIRE: FILESYSTEMS
# BEFORE:  netif
# KEYWORD: firstboot

/etc/installerconfig

Code:

...
#!/bin/sh
...
touch /firstboot
...

Executing a command via shell script.

bsaidus

YYY__

aragats

cracauer@

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