Commands using ps (300)

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To create files with specific permission:

Test sendmail
test if sendmail is installed and working.

delete at start of each line until character
GNU grep's PCRE(Perl-compatible regular expressions).

Easily decode unix-time (funtion)
More recent versions of the date command finally have the ability to decode the unix epoch time into a human readable date. This function makes it simple to utilize this feature quickly.

Cleanup debian/ubuntu package configurations
Sometimes, simpler is better.

Get My Public IP Address

Tail -f at your own pace
The -s option allows you to specify the update interval

Watch active calls on an Asterisk PBX
This handles when you have a single call or channel. Other commands will strip out the result if there is a single channel or call active because the output changes the noun to be singular instead of plural.

Create arbitrary big file full of zeroes but done in a second
If you want to create fast a very big file for testing purposes and you do not care about its content, then you can use this command to create a file of arbitrary size within less than a second. Content of file will be all zero bytes. The trick is that the content is just not written to the disk, instead the space for it is somehow reserved on operating system level and file system level. It would be filled when first accessed/written (not sure about the mechanism that lies below, but it makes the file creation super fast). Instead of '1G' as in the example, you could use other modifiers like 200K for kilobytes (1024 bytes), 500M for megabytes (1024 * 1024 bytes), 20G for Gigabytes (1024*1024*1024 bytes), 30T for Terabytes (1024^4 bytes). Also P for Penta, etc... Command tested under Linux.

Archive all files that have not been modified in the last days
Finally, we can make the file "unchangeable" sudo chattr +i


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