I’ve used find commands before and talked about them on Unixsupport.com, however I recently needed to stack a few find commands and found it less then easy to search out support… so:
find . \( -ctime +1 -not -ctime +3 \) | xargs -I{} ls -l {}
find files, in the current directory, that were created more then 1 day ago, not, more then 3 days ago, then send them over to ls to show them to me
So sometimes I’m on a box and need to test if a port is cleared on a firewall.. i may not yet have apache installed but I want to test if port 80 is open, or I may want to act as a server to grab a request..
simple with Netcat.
nc -l -p 8080
will open a listen on port 8080 and after the first connect, exit and go back to shell… useful for testing
Sometimes I’ve had to create files to test transfer speeds between points.. sure you could transfer that 650 meg iso image of freebsd, or you could create a “blank” file..
dd if=/dev/zero of=linux.ex2 bs=1024 count=131072
creates 128mb blank file
dd if=/dev/random of=linux.ex2 bs=1024 count=131072
creates 128mb file with random characters in it
for example.. play around with the count numbers in bytes and your set.
255.255.255.255 11111111.11111111.11111111.11111111 /32 Host (single address)
255.255.255.254 11111111.11111111.11111111.11111110 /31 Unusable
255.255.255.252 11111111.11111111.11111111.11111100 /30 4 IPs with 2 Usable
255.255.255.248 11111111.11111111.11111111.11111000 /29 8 IPs with 6 Usable
255.255.255.240 11111111.11111111.11111111.11110000 /28 16 IPs with 14 Usable
255.255.255.224 11111111.11111111.11111111.11100000 /27 32 IPs with 30 Usable
255.255.255.192 11111111.11111111.11111111.11000000 /26 64 IPs with 62 Usable
255.255.255.128 11111111.11111111.11111111.10000000 /25 128 IPs with 126 Usable
255.255.255.0 11111111.11111111.11111111.00000000 /24 256 IPs with 254 Usable
*”Class C”*
255.255.254.0 11111111.11111111.11111110.00000000 /23
255.255.252.0 11111111.11111111.11111100.00000000 /22
255.255.248.0 11111111.11111111.11111000.00000000 /21
255.255.240.0 11111111.11111111.11110000.00000000 /20
255.255.224.0 11111111.11111111.11100000.00000000 /19
255.255.192.0 11111111.11111111.11000000.00000000 /18
255.255.128.0 11111111.11111111.10000000.00000000 /17
255.255.0.0 11111111.11111111.00000000.00000000 /16
*”Class B”*
255.254.0.0 11111111.11111110.00000000.00000000 /15
255.252.0.0 11111111.11111100.00000000.00000000 /14
255.248.0.0 11111111.11111000.00000000.00000000 /13
255.240.0.0 11111111.11110000.00000000.00000000 /12
255.224.0.0 11111111.11100000.00000000.00000000 /11
255.192.0.0 11111111.11000000.00000000.00000000 /10
255.128.0.0 11111111.10000000.00000000.00000000 /9
255.0.0.0 11111111.00000000.00000000.00000000 /8
*”Class A”*
254.0.0.0 11111110.00000000.00000000.00000000 /7
252.0.0.0 11111100.00000000.00000000.00000000 /6
248.0.0.0 11111000.00000000.00000000.00000000 /5
240.0.0.0 11110000.00000000.00000000.00000000 /4
224.0.0.0 11100000.00000000.00000000.00000000 /3
192.0.0.0 11000000.00000000.00000000.00000000 /2
128.0.0.0 10000000.00000000.00000000.00000000 /1
0.0.0.0 00000000.00000000.00000000.00000000 /0
*IP space*
*Note:* The first and last IP of a series are *NOT* usable and the first
usable IP is normally set up for the router.
The 1st IP is the network address. The last IP is the broadcast address.
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