Commands cat chmod cp mv ls –l ls ls -a date export find grep mkdir rmdir more less rm sort sleep wc -L kill kill -L diff cd sort whence umask umask -s who bg fg ln ln -s tail tail -f head what who am I history exec nice arch chown mount umount Arithmetic



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Shell Command and Programming Language Quick Reference

Commands

cat


chmod

cp

mv



ls –l

ls

ls -a



date

export


find

grep


mkdir

rmdir


more

less


rm

sort


sleep

wc -l


kill

kill -l


diff

cd

sort



whence

umask


umask -S

who


bg

fg

ln



ln -s

tail


tail -f

head


what

who am i


history

exec


nice

arch


chown

mount


umount
Arithmetic expressions

<= - less than or equal to

>= - greater than or equal to



< - less than

> - greater than

== - equal to

!= - not equal to

* - multiplication

/ - division

+ - addition

- - subtraction


Shell variables used by ksh

PATH - Path search directories

SHELL - Pathname of the Shell

TERM - Terminal type

HOME - Your home directory

ENV - User environment file



Shell variables set by ksh

PWD - Working directory

LINENO - Current line number

PPID - Parent process id


Shell statements

printf “string” - output a string of information

echo $COUNTER - output content of the variable COUNTER

echo “Text line” - output text line to monitor from script

printf $NUMBER - output content of the variable NUMBER

NUMBER=$(($NUMBER-1)) - decrease NUMBER value by one

$# - number of positional parameters

$? - return value

$$ - process id of this shell

$! - background process id

$1 - first command line argument

$2 - second command line argument



Conditional Expression Primitives

-r - true if file exists and is readable

-w - true if file exists and is writable

-x - true if file exists and is executable

-f - true if file exists and is a file

-d - true if file exists and is a directory

-eq - true if value of exp1 and exp2 are equal

-ne - true if value of exp1 and exp2 are not equal

-gt - true if value of exp1 is greater than value of exp2

-ge - true if value of exp1 is greater than or equal to value of exp2

-lt - true if value of exp1 is less than value of exp2

-le - true if value of exp1 less than or equal to value of exp2


Quoting

‘ …’ - single literal quotes

“…” - double quotes (interpolation)

`…` - single back ticks (command execution)



I/O Operators

< Variable - read from file (cat < test_file)

> Variable - write to a file (cat > test_file)

Variable >> Variable - append content of file_1 to the end of file_2 (cat file_1 >> file_2)

& - Execute process in background



Syntax

while [ … ]

do



done


if [ … ]

then


fi
if [ … ]

then



elif



fi
test –r “$test_file”

test x+1 –gt y
AWK
The character "\" is used to "escape" or mark special characters. The list of these characters is in table below:
+-------------------------------------------------------+

| AWK Table 5 |

| Escape Sequences |

|Sequence Description |

+-------------------------------------------------------+

|\a ASCII bell (NAWK only) |

|\b Backspace |

|\f Formfeed |

|\n Newline |

|\r Carriage Return |

|\t Horizontal tab |

|\v Vertical tab (NAWK only) |

|\ddd Character (1 to 3 octal digits) (NAWK only) |

|\xdd Character (hexadecimal) (NAWK only) |

| Any character c |

+-------------------------------------------------------+

Let us create employee.txt file which has the following content, which will be used in the

examples mentioned below.


$cat employee.txt

100 Thomas Manager Sales $5,000

200 Jason Developer Technology $5,500

300 Sanjay Sysadmin Technology $7,000

400 Nisha Manager Marketing $9,500

500 Randy DBA Technology $6,000


Awk has number of built in variables. For each record i.e line, it splits the record delimited by whitespace character by default and stores it in the $n variables. If the line has 4 words, it will be stored in $1, $2, $3 and $4. $0 represents whole line. NF is a built in variable which represents total number of fields in a record.

$ awk '{print $2,$5;}' employee.txt

Thomas $5,000

Jason $5,500

Sanjay $7,000

Nisha $9,500

Randy $6,000
$ awk '{print $2,$NF;}' employee.txt

Thomas $5,000

Jason $5,500

Sanjay $7,000

Nisha $9,500

Randy $6,000



In the above example $2 and $5 represents Name and Salary respectively. We can get the Salary using $NF also, where $NF represents last field. In the print statement ‘,’ is a concatenator.
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