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Collection of Less Commonly Used UNIX Commands
September 11th, 2013 | Linux | System Administration | Technology

[ Check out my latest post on the HP Security Blog: “The Secure Web Series, Part 1: Securing The Password Reset Mechanism” ]

unixcommands

Over at Hacker News there are often threads about less-traveled UNIX commands. One particular comment collected a few of the posts, and I decided to parse all of those threads’ commands, plus my own favorite list of obscure entries, and put them in one place.
Somewhat obscure UNIX commands

column: create columns from text input
tr: translate/substitute/delete input
join: like a database join but for text
comm: file comparison like a db join
paste: put lines in a file next to each other
rs: reshape arrays
jot: generate data
expand: replace spaces and/or tabs
time: track time and resourcing
watch: execute something on a schedule in realtime
xargs: execute something on all inputs
iftop: visually show network traffic
jnettop a more detailed iftop
htop: show system stats more powerfully
xxd: manipulate files in hex
mtr: powerful traceroute replacement
mdfind: osx find replacement that uses spotlight
brew: osx package manager
df: disk free
du: disk usage
iotop: i/o stats
dig: dns queries
host: dns queries
man ascii: lookup your ascii
sshfs: mount a directory through ssh
wget: get w’s
dstat: powerful system statistics
tmux: a better screen
jq: command line JSON parsing
pushd: push your pwd to a stack
popd: pop pwd off your stack
lsof: godlike system information [*]
ncat: nmap-based replacement for nc
fuser: kills locking processes
vim: attack yourself
tac: cat in reverse
slurm: network interface stats
rename: change spaces to underscores in names
bmon: a simple bandwidth monitor
open .: in osx, open finder in the current dir
lsmod: show kernel modules
printf: change the format of output
timeout: execute something and kill it soon after
disown: protect a job from disconnect
fc: edit your last command in your editor and execute it
sudo !!: repeat last command with sudo
tee: send output to stdout as well
pgrep: greps through processes
pkill: kills processes based on search
fmt: text formatter
multitail: see logs in separate views
bc: an interactive calculator language
apropos: info on commands
strace: the uber debug tool
man units: interesting
pstree: shows processes in a…well…tree
pv: a progress bar for piped commands
ddate: wtf
zgrep: grep within compressed files
zless: look at compressed files
nping: nmap-based custom packet creation
readlink: read values of links
iostate: look at your disk i/o
atop: another top
split: break a file into pieces
dd: disk writing
ndiff: show differences in nmap scans
ss: socket statistics (show apps using the Internet)

via blue again, to read !

mis en test sur coin, a surveiller

You can substitute the value of $i in to see the exact command you're trying to run:

app4/ | sed -e "s/^.*(.)$/\1/"

This doesn't work because app4/ isn't a command. You're trying to pipe app4/ into sed, so you need to use something that outputs app4/:

echo app4/ | sed -e "s/^.*(.)$/\1/"

This works, but you don't really need to use sed for this; bash has quite a few string manipulation tools. For example, ${i#} will give you the length of $i, and ${i:j} will give you a substring starting at j, so ${i:$((${i#}-1))} will give you the last character.

The easiest way to do what you're trying is probably with ${i%/}. This will return $i, but will strip off a / from the end if there is one:

$ i="app4"; echo ${i%/}
app4
$ i="app4/"; echo ${i%/}
app4

Thus:

if [ "${i%/}" = "$i" ]
then
echo "file"
else
echo "folder"
fi

However, if all you really want is to know if $i is a valid directory, you can just use:

if [ -d "$i" ]

'faut que je finisse de lire ces docs