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run command on a group of nodes in parallel

Read aloud a text file in Ubuntu (and other Unixes with espeak installed

Show top 50 running processes ordered by highest memory/cpu usage refreshing every 1s
http://alvinalexander.com/linux/unix-linux-process-memory-sort-ps-command-cpu for an overview of --sort available values

Efficiently print a line deep in a huge log file
Sed stops parsing at the match and so is much more effecient than piping head into tail or similar. Grab a line range using $ sed '999995,1000005!d' < my_massive_file

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" }

print all characters of a file using hexdump
'od -c' works like 'hexdump -c' but is available on other operating systems that don't ship with hexdump (e.g. solaris).

Count the total number of files in each immediate subdirectory
counts the total (recursive) number of files in the immediate (depth 1) subdirectories as well as the current one and displays them sorted. Fixed, as per ashawley's comment

cd to (or operate on) a file across parallel directories
This is useful for quickly jumping around branches in a file system, or operating on a parellel file. This is tested in bash. cd to (substitute in PWD, a for b) where PWD is the bash environmental variable for the "working directory"

sort lines by length

Generate MD5 of string and output only the hash checksum in a readable format
Generates the md5 hash, without the trailing " -" and with the output "broken" into pairs of hexs.


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