The Shell

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The Shell
Parameters and Variables
The Bourne Again Shell
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The Shell

 

 The command line

          The shell interprets and executes a command when you type it at its prompt.

          After your press enter the shell scans the command line for proper syntax

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UNIX shell differences and how to change your shell 

Arguments

          Arguments can be filename, string of text, number or some other object that a command requires or act on.

 

Options

          An option is an argument that modifies the effects of a command

          IE. ls –la

 

Processing the command line

          CONTROL-H (erase a character)

          CONTROL-U (kill a line)

          CONTROL-W (erase a word)

 

          $ls

          $/bin/ls

 

Standard input and standard output

 

          Your terminal is a device file under /dev, if you type tty and it shows /dev/pts/3 it would be the pathname to your terminal.

          Standard output would be the terminal

 

          cat  command can be used as both Standard input and standard output

 

          IE.  cat    (by itself  will echo what you type. CTRL-D sends an end of file)

                        cat filename

cat < filename (redirecting standard input) Other commands lpr, sort, grep

cat > filename

cat firstfile secondfile > thirdfile


 

Appending Standard output to a file

         

          cat pear >> orange

               

[wmorales@rc33uxas01 wmorales]$ date > whoison

[wmorales@rc33uxas01 wmorales]$ cat whoison

Wed Feb  2 12:21:11 PST 2000

[wmorales@rc33uxas01 wmorales]$ who >> whoison

[wmorales@rc33uxas01 wmorales]$ cat whoison

Wed Feb  2 12:21:11 PST 2000

klulla   pts/0    Feb  2 10:14 (PPPa2-ResalePortlandOr4-3R7161.saturn.bbn.com)

klulla   pts/5    Feb  2 10:49 (PPPa61-ResalePortlandOr2-3R7170.saturn.bbn.com)

jtaylor  pts/2    Feb  2 11:50 (216-99-207-77.cust.aracnet.com)

bjensen  pts/6    Feb  2 12:11 (198.106.33.106)

ehumphre pts/1    Feb  2 10:27 (fw1.tek.com)

wmorales pts/3    Feb  2 09:42 (198.106.33.204)

dmichels pts/9    Feb  2 11:07 (198.106.33.210)

klulla   pts/4    Feb  2 12:27 (PPPa10-ResalePortlandOr2-3R7170.saturn.bbn.c

om)

[wmorales@rc33uxas01 wmorales]$

 

 

/dev/null

          place to redirect output that you do not want

 

PIPES

 

          ls | more

 

          tr sting1 sring2  (translate utility)

A  common  use of tr is to convert lowercase characters to uppercase.  This can be done in many ways.  Here are three of them:

              tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ

              tr a-z A-Z

              tr '[:lower:]' '[:upper:]' 

         

          cat abastract | tr abc ABC   

 

          ls | lpr


 

FILTER

 

          A command that processes an input stream of data to produce an output stream of data

 

          who | sort | lpr

 

tee utility

 

          read from standard input and write to standard output and files

               

[wmorales@rc33uxas01 wmorales]$ who | tee whoison.out | grep wmorales

wmorales pts/3    Feb  2 09:42 (198.106.33.204)

[wmorales@rc33uxas01 wmorales]$ cat whoison.out

klulla   pts/0    Feb  2 10:14 (PPPa2-ResalePortlandOr4-3R7161.saturn.bbn.co

m)

klulla   pts/5    Feb  2 10:49 (PPPa61-ResalePortlandOr2-3R7170.saturn.bbn.c

om)

jreynold pts/7    Feb  2 12:32 (pdx10-7-58.transport.com)

ggrassma pts/2    Feb  2 13:00 (198.106.33.161)

bjensen  pts/6    Feb  2 12:11 (198.106.33.106)

ehumphre pts/1    Feb  2 10:27 (fw1.tek.com)

wmorales pts/3    Feb  2 09:42 (198.106.33.204)

mmcgillv pts/8    Feb  2 12:49 (atropos.jf.intel.com)

[wmorales@rc33uxas01 wmorales]$

 

 

 

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This page was last modified September 26, 2004
wmorales@pcc.edu