Cli on tech.notes

OCR all PDFs in a folder by cron

Mon, 03 Jul 2023 08:27:56 +0000

I will not write a long explanation, just this short one.

The cronjob looks like this:

* * * * * sh -c 'flock -n /tmp/my.lockfile /home/user/scripts/ocr_pdf_scan.sh'

This will start sh (a shell, just like bash) and run the command after -c. The command flock will create a lock-file, to prevent that this cron job is started while there is still the previous cron jobs running.

The cron job runs every minute, so in crontab it has * * * * * (five stars in front of the command).

rename

Mon, 29 Apr 2019 20:06:29 +0000

… is an easy to use and powerful tool, it can be used to replace part of file name (string1) with some other string. Something one can also do with some “sed” hack, but this tool is much easier to use, especially for beginners.

You can get all information needed from “rename –help” (here from Linux Mint):

rename --help
Usage:
    rename [ -h|-m|-V ] [ -v ] [ -n ] [ -f ] [ -e|-E perlexpr]*|perlexpr
    [ files ]

Options:
    -v, -verbose
            Verbose: print names of files successfully renamed.

    -n, -nono
            No action: print names of files to be renamed, but don't rename.

    -f, -force
            Over write: allow existing files to be over-written.

    -h, -help
            Help: print SYNOPSIS and OPTIONS.

    -m, -man
            Manual: print manual page.

    -V, -version
            Version: show version number.

    -e      Expression: code to act on files name.

            May be repeated to build up code (like "perl -e"). If no -e, the
            first argument is used as code.

    -E      Statement: code to act on files name, as -e but terminated by
            ';'.

I did use this tool rename some files that contained the string “www”, which I had to replace with “web”, lets say there were files named like this:

Resize qemu VM disk

Sat, 16 Mar 2019 22:48:48 +0000

VM runterfahren

Image der VM vergrössern:

sudo qemu-img resize /var/lib/libvirt/images/vm_disk.img +15GB

Je nach Setup ist sudo nicht nötig, durch den Befehl wird die Diskimagedatei um 15 GB vergrößert.

VM starten

Weiter geht es in der VM auf der Konsole.

Partitioen mit parted anzeigen lassen:

parted -l

Ausgabe so oder ähnlich:
Model: Virtio Block Device (virtblk)
Disk /dev/vda: 53,7GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number Start End Size Type File system Flags
1 1049kB 53,7GB 53,7GB primary btrfs boot

explainshell.com

Sat, 16 Mar 2019 21:09:38 +0000

Did you know explainshell.com yet? Try it, for example with that command from last time

sudo lsof -i -P -n | grep LISTEN

this is an amazing web site I use often so see what commands do that I find somewhere. Try it.