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preprocess code to be posted in comments on this site
Assuming that $script contains the filename of a script you'd like to post as part of a comment on this site, this will prefix each line with '$' and pipe it into the X selection. From there just put the cursor in the right place in the comments box and middle-click. Should work pretty much anywhere with xclip installed. On debian-ish systems this is installed as part of the package "xclip".

find all active IP addresses in a network
I just added the args [arp-scan --localnet] which works for Debian users, because the package 'arp' has name 'arp-scan', and it doesn't works with the argument 'arp'.

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

Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)
Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

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" }

How to secure delete a file
Instead, install apt-get install secure-delete and you can use: -- srm to delete file and directory on hard disk -- smem to delete file in RAM -- sfill to delete "free space" on hard disk -- sswap to delete all data from swap

Know which modules are loaded on an Apache server
This let you know which modules has loaded the Apache server, very useful to know if the mod_rewrite is ready to use.

retrieve the source address used to contact a given host
on multihomed hosts, connected to several networks, could be usefull to know the source address (local ip address) used to reach the target host, this command does not require root priviledges. The command use a TCP socket, if there is any error the command return an empty string, elsewhere return a valid ip address.

detect the fastest ldap server on a intranet
This command line detect ldap hosts, by mandatory dns entry, then ping them to detect response average. based on ping response average it sorts and print the faster server in first output line

Easy file sharing from the command line using transfer.sh
Requires: curl xsel access to the internet(http://transfer.sh) This is an alias utilizing the transfer.sh service to make sharing files easier from the command line. I have modified the alias provided by transfer.sh to use xsel to copy the resulting URL to the clipboard. The full modified alias is as follows since commandlinefu only allows 255 characters: transfer() { if [ $# -eq 0 ]; then echo "No arguments specified. Usage:\necho transfer /tmp/test.md\ncat /tmp/test.md | transfer test.md"; return 1; fi if tty -s; then basefile=$(basename "$1" | sed -e 's/[^a-zA-Z0-9._-]/-/g'); curl --progress-bar --upload-file "$1" "https://transfer.sh/$basefile" |xsel --clipboard; else curl --progress-bar --upload-file "-" "https://transfer.sh/$1" |xsel --clipboard ; fi; xsel --clipboard; }


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