One-liner: Decompress file and diff against another file
Dec 8th, 2016 by miki

Below is a handy shell one-liner for comparing the decompressed contents of a compressed file against a plain file. The purpose here is to test whether the compressed file is actually derived from compressing the plain file. This particular example is from a real life situation where log rotation by cron.daily on a Ubuntu server had begun failing. The situation is thought to be the result of an interrupted logrotate execution leaving a compressed (but non-rotated) intermediate file in the file system that prevented further log rotation on subsequent executions.

The command constructs a pipe between two process, specified using the | symbol (vertical line), to send the decompressed contents from gunzip stdout to stdin of the compare tool. The example uses diff as compare tool which is suitable for textual contents. You could use f.x. cmp instead if the contents is binary. Both diff and cmp interprets the file name “-” as meaning that input should be read from stdin.

$ gunzip --stdout /var/log/syslog.1.gz | diff --report-identical-files - /var/log/syslog.1
Files - and /var/log/syslog.1 are identical

The above uses long options for clarity, in a real life situation you would probably be using short options instead. That means -c instead of –stdout and s instead of –report-identical-files.

$ gunzip -c /var/log/syslog.1.gz | diff -s - /var/log/syslog.1
Files - and /var/log/syslog.1 are identical


Huawei E1752 on Ubuntu 10.04
Jun 26th, 2010 by miki

Today I managed to get a Huawei E1752 3G modem (USB id 12d1:1446/140c, usually called E1552 by lsusb) running on Ubuntu 10.04 without all the hassle described elsewhere (see this, this or this or this …).

This particular modem came from the danish cable ISP YouSee, in an offering known as Mobilt Bredbånd (mobile broadband), targeting their existing cable internet customers. Pricing starts at lowest offering of 1 Mbit/384 kbit transmission speed with 1GiB/month data limit at DKK 99/month (~USD 16.5 ~EUR 13.3).

As many recent USB modems, this one is a mode switching type with multiple personalities (Option ZeroCD(TM)). At plugin it defaults to an emulated CD mass storage drive (USB ID 12d1:1446), with an onboard Windows driver and dialer (Mobile Partner). When detected by a driver knowing it’s schizophrenic nature, it can be manipulated, utilizing psychotherapeutic tricks, to switch it’s personality to the modem it actually is (USB ID 12d1:140c). Hence, on non-Windows systems some magic needs to be established to make the modem actually behave like a modem.

One incarnation (se discussion about other stuff here) of this magic is called usb_modeswitch. That is also the solution chosen by the Ubuntu distribution team, and it is present in the repositories and configured for the Huawei E1752 in Ubuntu 10.04 ‘Lucid Lynx’, so we just need to know that we need it. You do now…

Activating usb_modeswitch is a matter of installing the usb-modeswitch package. Find it in Synaptic or issue the following in a terminal:

sudo apt-get install usb-modeswitch

Now all you have to do is insert the modem and check (we like to be certain, right?) with lsusb that you have the 12d1:140c modem device instead of the 12d1:1446 mass storage device.

The Gnome Network Manager should now pick up on the new modem device, and offer you the possibility of adding a new mobile broadband connection. In my case, it defaulted to an Oister connection, but removing that and using the wizard to create a TDC connection (YouSee is a part of/close associate of TDC) did the trick, after reinserting the modem once more.

Now I wonder why my own E160G modem works without usb_modeswitch installed…

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