jan07c.docx

SHELL PROGRAMMING Desktop Downloads Movies Pictures testdir  Why Unix Documents Library Music Public o Available on number of platforms $ cd testdir $ ls o Multi-user, multi-programmed asdf o Shares computer resources sensibly $ cd .. # exit test dir directory o Permits manipulation of files, processes and programs o Allows inter-process and inter-machine communication $ rmdir testdir rmdir: testdir: Directory not empty o Permits access to its operating features $ cd testdir o The unix philopshy: rm asdf  Write programs that do one thing and do it well $ cd .. # exit test dir directory  Write programs to work together $ rmdir testdir  Write programs that handle text streams, because it’s a Desktop Downloads Movies Pictures universal interface Documents Library Music Public  Software Tools  cat – concatenate and print given files o A good tool does one or two basic things well  does not change the files o A good tool can be combined w/ other good tools $ cat faculty Craig, Michelle o Principles: Craig, Mike  Do one basic thing well  With some basic variations O'Neil, Craig  Simple input formats Reid, Karen Gries, Paul  Plain text Craigleith, Jim  Don’t require interactive input Horton, Diane  Simple output format Campbell, Jennifer  Expected to be input to another tool Heap, Danny  Shell, a program that can execute another program  for concatenation see example under st input/st output o The % is the shell prompt for csh, the $ is the shell prompt for  sort – sort the lines of text files o Shells  can give a file name to sort the file or sort standard input  Accept commands (programs) as input from user entered strings  Finds the executable $ sort faculty # sorting file  Interprets the arguments Campbell, Jennifer  Starts executing the command Craig, Michelle o Shells also have some “built-in” commands Craig, Mike o Comments indicated by strings after # Craigleith, Jim $ ls #this is a comment Gries, Paul Heap, Danny Week1-2-Shell.key Week1-Intro.key faculty sorted_faculty topics.pages Horton, Diane o Common commands (tools) in shell O'Neil, Craig  Echo – write arguments to standard output Reid, Karen echo this is standard output $ sort # sort standard input this is standard output This is # the input fun  ls – list directory contents isn't  if no path following, lists working directory it? # stop input by ctrl-D $ ls Week1-2-Shell.key Week1-Intro.key Fun # the sorted order faculty sorted_faculty topics.pages isn't it? $ ls /Users/Yan This is Desktop Downloads Movies Pictures $ sort –k 2 # sort second character Documents Library Music Public aaaa z # the input  pwd – return working directory name bbbb y $ pwd /Users/Yan bbbb x # the sorted cccc y  cd – built in command, change directory  Standard input/standard output  cd or cd ~ changes working directory to home  Most commands has a standard output, which can be directory, ~ is sort for home directory piped into other commands or be saved as a file  cd . doesn’t change working directory since . is short  Pipes (explained later) for current working directory  Used > to save to a file, must be new  cd .. moves up one directory $ sort faculty > new_sorted_faculty  cd – switch ot previously opened directory $ cat new_sorted_faculty  mkdir – make directories Campbell, Jennifer Craig, Michelle $ ls Desktop Downloads Movies Pictures Craig, Mike Documents Library Music Public Craigleith, Jim $ mkdir testdir Gries, Paul $ ls Heap, Danny Desktop Downloads Movies Pictures testdir Horton, Diane Documents Library Music Public O'Neil, Craig Reid, Karen  rmdir – removes directory, must be empty $ echo this is file1 > file1 $ ls $ cat file1 this is file1 tg pts/11 Jan 8 15:40 (206- $ echo what does this do? > file2 248-190-13.dsl.teksavvy.com) $ cat file2 mcraig pts/6 Jan 9 17:13 (red- what does this do? gw71.cs.toronto.