Working with the Unix OS

Unix Tools
awk '$3 > 0 { print $1, $2 * $3 }' employee.data
Mark 85
Sue 180
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UBUNTU: mawk
Usage: mawk [-W option] [-F value] [-v var=value] [--] 'program text' [filename]
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! Program structure
pattern ( action )
every input line is tested using 'pattern'
! Running AWK
awk 'program' input files
awk -f progfile input files
! Output
{ print $0 } print entire line
{ print $1, $3 } print first and third fields
{ print NF, $1, $NF }print number of fields and first and last fields
{ print NR, $0 } print number of records and line prefix each line with line number
{ printf("pay for", $1, "is", $2 * $3) } place text in output
{ printf("pay for %-8s is $%6.2f\n", $1, $2 * $3) } formatted output
! Selection
$2 >= 5
$1 == "Sue"
/Sue/
$2 >= 4 || $3 >= 20
!($2 < 4 && $3 < 20)
# data validation
NF != 3 {print $0, "number of fields is not equal to 3"}
$2 < 5 {print $0, "rate is below minimum wage"}
$3 < 0 {print $0, "negative hours worked"}
$3 > 60 {print $0, "too many hours worked"}
# add headings to input file
BEGIN {print "NAME RATE HOURS", print ""}
{ print }
! Computing
$3 > 15 { emp = emp + 1 }
END { print emp, "employees worked more than 15 hours" }
END { print NR, "employees"}
{ pay = pay + $2 * $3 }
END { print NR, "employees"}
print "average pay is", pay/NR
}
$2 > maxrate { maxrate = $2; maxemp = $1 }
END { print "highest hourly rate:", maxrate, "for", maxemp }
# string concatenation
{ names = names $1" "}
END { print names }
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