Hi Aitor!

Anno domini 2019 Tue, 19 Mar 09:56:07 +0100
aitor_czr scripsit:
> Hi Nick,
>
> On 19/3/19 9:21, Dr. Nikolaus Klepp wrote:
> > You might call me ignorant, but with bash this can be done a bit simpler (this is from my solution to the detect-if-kable-present-while-booting-problem):-)
> >
> > #!/bin/bash
> >

> > while sleep 1; do
> >      for i in /sys/class/net/eth*; do
> >          VAR=$(basename $i)
> >          VAL=$(sed -n 's/0/UN/p' $i/carrier)PLUGGED
> >          if [ "${!VAR}" != "$VAL" ]; then
> >              echo $VAR $VAL
> >              declare $VAR=$VAL
> >          fi
> >      done
> > done

> >
> >
> > Nik
> Thanks for your script! Interesting to know... With a short look, i
> seems to read the value content in the /sys/class/eth0/carrier file, set
> to "0" or "1".
> I was thinking about this possibility a couple of days ago, but i'm not
> pretty sure if its value also depends on the status of the network
> hotpluggable device. I'm testing it...

Interestingly the "carrier"-column in /proc/net/dev does not correspond to the cable beeing plugged in or not, it's always "0" on my computer.

Nik


> On the other hand, here you are the code used in the ethtool-lite.c file
> of the netcfg udeb package used by debian-installer, doing something
> similar (in the case of the FreeBSD kernel
> it uses a raw socket instead):
>
>     int len = strlen(SYSCLASSNET) + strlen(iface) + strlen("/carrier") + 1;
>     char* filename = malloc(len);
>     snprintf(filename, len, SYSCLASSNET "%s/carrier", iface);
>     FILE* fp = fopen(filename, "r");
>     free(filename);
>
>     char result[2];
>     if (fgets(result, sizeof(result), fp) == NULL) {
>         fclose(fp);
>         if (errno == EINVAL) {
>             di_info("ethtool-lite: %s is down", iface);
>             return DISCONNECTED;
>         }
>         di_error("ethtool-lite: getting carrier failed: %s",
>             strerror(errno));
>         return UNKNOWN;
>     }
>     fclose(fp);
>
>     switch (result[0]) {
>     case '1':
>         di_info("ethtool-lite: %s: carrier up", iface);
>         return CONNECTED;
>     case '0':
>         di_info("ethtool-lite: %s: carrier down", iface);
>         return DISCONNECTED;
>     }
>     di_info("ethtool-lite: %s: could not determine carrier state; got
> \"%s\"",
>         iface, result);
>     return UNKNOWN;
>
> Cheers,
>
> Aitor.





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