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Remove all zero size files from current directory (not recursive)

View a file with less, starting at the end of the file
The same as typing 'less filename' then 'G' or '>' or the END key. Comes in handy with shell scripts or aliases: alias weblog='less +G /var/log/httpd/access_log' alias errlog='less +G /var/log/httpd/error_log'

Router discovery

Download SSL/TLS pem format cert from https web host

Copy input sent to a command to stderr
In the above example 'muspi merol' (the output of the first rev command) is sent to stderr and 'lorem ipsum' (the output of the second rev command) is sent to stdout. rev reverse lines of a file or files. This use of tee allows testing if a program correctly handles its input without using files that hold the data.

Remove everything except that file
it will remove everything except the file names matching you can use also use wildcards

Find and delete oldest file of specific types in directory tree
This works on my ubuntu/debian machines. I suspect other distros need some tweaking of sort and cut. I am sure someone could provide a shorter/faster version.

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Rename files in batch

Set access and modification timestamps of a file using another one as reference
atime and mtime timestamps of $FILE2 is changed according to the ones of $FILE1. If $FILE2 doesn't exist is created.


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