Commands using dmesg (15)

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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" }

copy/mkdir and automatically create parent directories
The --parents option will cause cp or mkdir to automatically create the parent directory structure. $mkdir --parents /one/two/three/dir will create /one, /one/two, and /one/two/three as needed before creating dir. cp will copy files with their full directory structure into the target directory with this option. Thanks to Peter Leung at: http://linuxcommando.blogspot.com/2007/11/use-of-parents-flag-in-mkdir-and-c.html which has good examples of usage.

find out how much space are occuipied by files smaller than 1024K
The command gives size of all files smaller than 1024k, this information, together with disk usage, can help determin file system parameter (e.g. block size) or storage device (e.g. SSD v.s. HDD). Note if you use awk instead of "cut| dc", you easily breach maximum allowed number of records in awk.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Generic shell function for modifying files in-place
Some commands (such as sed and perl) have options to support in-place editing of files, but many commands do not. This shell function enables any command to change files in place. See the sample output for many examples. The function uses plain sh syntax and works with any POSIX shell or derivative, including zsh and bash.

Quick access to ASCII code of a key

Show errors in the kernel ring buffer
Much more useful then parsing syslog

Convert CSV to JSON
Replace 'csv_file.csv' with your filename.

Rename files in batch

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

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