Introduction to Bash/Shell (Continued)

-

File Commands (continued)

wc <filename> tells you how many lines, words and characters there are in a file

chmod -options <filename> lets you change the read, write, and execute permissions on your files

gzip <filename> compresses files

gunzip <filename> uncompresses files compressed by gzip

gzcat <filename> lets you look at gzipped file without actually having to gunzip it

File Commands (continued)

lpq check out the printer queue

lprm <jobnumber> remove something from the printer queue

genscript converts plain text files into postscript for printing and gives you some options for formatting

dvips <filename> print .dvi files (i.e. files produced by LaTeX)

grep <pattern> <filenames> looks for the string in the files

grep -r <pattern> <dir> search recursively for pattern in directory

SSH, System Info & Network Commands

ssh user@host # connects to host as user ssh -p user@host # connects to host on specified port as user ssh-copy-id user@host # adds your ssh key to host for user to enable a keyed or passwordless login

whoami # returns your username passwd # lets you change your password quota -v # shows what your disk quota is date # shows the current date and time cal # shows the month’s calendar uptime # shows current uptime w # displays whois online finger # displays information about user uname -a # shows kernel information man # shows the manual for specified command df # shows disk usage du # shows the disk usage of the files and directories in filename (du -s give only a total) last # lists your last logins ps -u yourusername # lists your processes kill # kills (ends) the processes with the ID you gave killall # kill all processes with the name top # displays your currently active processes bg # lists stopped or background jobs ; resume a stopped job in the background fg # brings the most recent job in the foreground fg # brings job to the foreground

ping # pings host and outputs results whois # gets whois information for domain dig # gets DNS information for domain dig -x # reverses lookup host wget # downloads file

Input/Output Redirectors.

cmd1|cmd2 pipe; takes standard output of cmd1 as standard input to cmd2 > file directs standard output to file < file takes standard input from file >> file directs standard output to file; append to file if it already exists >|file forces standard output to file even if noclobber is set n>|file forces output to file from file descriptor n even if noclobber is set <> file uses file as both standard input and standard output n<>file uses file as both input and output for file descriptor n <<label here-document n>file directs file descriptor n to file n<file takes file descriptor n from file n>>file directs file description n to file; append to file if it already exists n>& duplicates standard output to file descriptor n n<& duplicates standard input from file descriptor n n>&m file descriptor n is made to be a copy of the output file descriptor n<&m file descriptor n is made to be a copy of the input file descriptor &>file directs standard output and standard error to file <&- closes the standard input >&- closes the standard output n>&- closes the ouput from file descriptor n n<&- closes the input from file descriptor n

Process Handling

To suspend a job, type CTRL+Z while it is running. You can also suspend a job with CTRL+Y.
This is slightly different from CTRL+Z in that the process is only stopped when it attempts to read input from terminal.
Of course, to interrupt a job, type CTRL+C.

myCommand & runs job in the background and prompts back the shell

jobs lists all jobs (use with -l to see associated PID)

fg brings a background job into the foreground fg %+ brings most recently invoked background job fg %- brings second most recently invoked background job fg %N brings job number N fg %string brings job whose command begins with string fg %?string brings job whose command contains string

kill -l returns a list of all signals on the system, by name and number kill PID terminates process with specified PID

ps prints a line of information about the current running login shell and any processes running under it ps -a selects all processes with a tty except session leaders

trap cmd sig1 sig2 executes a command when a signal is received by the script trap "" sig1 sig2 ignores that signals trap - sig1 sig2 resets the action taken when the signal is received to the default

disown <PID|JID> removes the process from the list of jobs

wait waits until all background jobs have finished

tar xvzf passwd reset special notations (. and ..) file tree history grep input/output redirection ps du df uptime vi basics scp md5