Class Notes (839,315)
Canada (511,260)
CSC209H1 (41)
Karen Reid (20)
Lecture

jan11c.docx

2 Pages
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Department
Computer Science
Course Code
CSC209H1
Professor
Karen Reid

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Description
 Pipelining commands – move to jan07c $ $name  Background processes – moved to jan09c -bash: Carl: command not found $ ls  Which cell? Week1-2-Shell.key file2 o sh – Bourne shell my_first_shell_script  Most common, other shells are a superset Week1-Intro.key file3 outer both filelist  Good for programming
 sorted_faculty o csh or tcsh – command-line default on CDF eveningClass filelongname  C-like syntax
Best for interactive use this.is.a.legal.filename  not good for programming faculty first_name_first o bash – default on Linux (Bourne again shell) topics.pages  based on sh, with some csh features. file1 lecture_part2_script $ prog=my_first_shell_script  Shell programming $ $prog o Commands run from a file in a subshell today is our first lecture o A great way to automate a repeated sequence of commands. michelle still feels like she is in portugal o File starts with #!/bin/sh  absolute path to the shell program o Loops  not the same on every machine. for i in 1 2 3 4; do echo $i o Can also write programs interactively by starting a new shell at the done command line. o Tip: this is a good way to test your shell program iters="1 2 3 4" for i in $iters; do o Ex. the same code ran in file/command line echo $i done  In a file #!/bin/sh $ ls echo "Hello World!" Week1-2-Shell.key file1.c filelist sorted_faculty  At the command line Week1-Intro.key file2 filelongname this.is.a.legal.filename skywolf% sh sh-2.05b$ echo "Hello World" both file2.c first_name_first Hello World topics.pages sh-2.05b$ exit eveningClass file3 lecture_part2_script exit faculty file3.c my_first_shell_script skywolf% file1 file4.c outer $ ls *.c file1.c file2.c file3.c file4.c o Commands $ for i in 4 5 6 7  You can run any program in a shell by calling it as you would on > do command line > echo why would I do this $i times > f$i.silly > done  When you run a program like grep or ls in a shell program, a new process is created. $ ls *.silly  There are also some built-in commands where no new process is f4.silly f5.silly f6.silly f7.silly $ cat *.silly created: why would I do this 4 times echo exit why would I do this 5 times set test why would I do this 6 times read shift why would I do this 7 times $ iters="1 2 3 4" o Variables $ for i in $iters  Varname=value (no spaces) > do  $varname to dereference > echo $i  Environment variables are global variables, can be used in a shell done  Ex. $SHELL 1 2  Variables here aren’t pointers to a memory location 3  Simply does text replacement/string replacement 4 $ for i in foo bar silly  Variables hold strings effectively, no floating point > do  Local variables disappears when shell terminates > echo $i  ex. > done bindir="/usr/bin" searchdirs="~/tests $HOME/test2 ." foo bar name=Carl silly $ echo name $ man seq name $ seq 2 10 $ echo $name 2 Carl 3 $ neighbour = Katrina 4 -bash: neighbour: command not found 5 $ neighbour=Ka
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