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find large files

Merge PDFs into single file

Prepend a text to a file.
The original command is great, but I often want to prepend to every line.

Wait for file to stop changing
This loop will finish if a file hasn't changed in the last 10 seconds. . It checks the file's modification timestamp against the clock. If 10 seconds have elapsed without any change to the file, then the loop ends. . This script will give a false positive if there's a 10 second delay between updates, e.g. due to network congestion . How does it work? 'date +%s' gives the current time in seconds 'stat -c %Y' gives the file's last modification time in seconds '$(( ))' is bash's way of doing maths '[ X -lt 10 ]' tests the result is Less Than 10 otherwise sleep for 1 second and repeat . Note: Clever as this script is, inotify is smarter.

Set a Reminder for yourself via the notification system
This will be seen through your system's visual notification system, notify-osd, notification-daemon, etc. --- sleep accepts s,m,h,d and floats (date; sleep .25m; date) --- notify-send (-t is in milliseconds && -u low / normal / critical) man notify-send for more information --- notification-daemon can use b/i/u/a HTML

retrieve the source address used to contact a given host
on multihomed hosts, connected to several networks, could be usefull to know the source address (local ip address) used to reach the target host, this command does not require root priviledges. The command use a TCP socket, if there is any error the command return an empty string, elsewhere return a valid ip address.

Router discovery

Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)
Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

seq (argc=2) for FreeBSD

Get a list of IP Addresses that have failed to login via SSH
This command shows a sorted list of the IP addresses from which there have been authentication errors via SSH (possible script kiddies trying to gain access to your server), it eliminates duplicates so it's easier to read, but you can remove the "uniq" command at the end, or even do a "uniq -c" to have a count of how many times each IP address shows in the log (the path to the log may vary from system to system)


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