cs534: more AWK stuff

Errors

This will CERTAINLY earn you a run-time error

gawk '{ printf("%-8s $%7.2f\n", $1, $2 * $3)]' emp.dat

Simple Output

printing every line

gawk '{ print( $0) }' emp.dat

will do the same as this

gawk '{ print }' emp.dat

printing certain fields

gawk '{ print( $1, $3) }' emp.dat

will print columns 1 and 3 from the entire file

NF, the number of fields

gawk '{ print( NF, $1, $NF) }' emp.dat

will print the number of fields, and the first and last field of each record

Computing and printing

gawk '{ print( $1, $2 * $3) }' emp.dat

will print the first field, followed by the multiplication of fields $2 and $3 of each record

(printf_allPay.bash)

Printing Line Numbers

gawk '{ print( NR, $0) }' emp.dat

will print a record number (line number) before each record

(printf_lineNums.bash)

Adding text to the output

gawk '{ print "Total pay for ", $1, " is ", $2 * $3 }' emp.dat

will print "Total pay for " before each calculated record

(printf_calcTxt.bash)

Fancier (cleaner) output

gawk '{ printf("Total pay for %-8s is $%7.2f\n", $1, $2*$3 ) }' emp.dat

will print same as above but WAY cleaner output

(printf_evenCleaner.bash)

Sorting output

gawk '{ printf(" $%7.2f %s\n", $2*$3, $0 ) }' emp.dat | sort

will print a sorted listing

(printf_sort1.bash)

Selection by Comparison

gawk '$2 >= 5' emp.dat

selection based on expression above

(printf_select1.bash)

Selection by Computation

gawk '$2 * $3 > 50 { printf("$%.2f for %s\n", $2 * $3, $1) }' emp.dat

selection based on expression above

(printf_select2.bash)

Selection by Text Content

gawk '$1 == "Suzie" 'emp.dat

selection based on the string above

(printf_select3.bash)

Data Validation

gawk 'NF != 3{ print( $0, "number of fields is not equal to 3") }' corrupt_emp.dat
gawk '$2 < 3.35{ print( $0, "rate is below minimum wage") }' corrupt_emp.dat
gawk '$2 > 10{ print( $0, "rate exceeds $10 per hour") }' corrupt_emp.dat
gawk '$3 < 0{ print( $0, "negative horus worked") }' corrupt_emp.dat
gawk '$3 > 60{ print( $0, "too many hours worked") }' corrupt_emp.dat

selection(s) based on the expressions above

(printf_select4.bash)

BEGIN

• The special pattern BEGIN matches before the first line of the first input file is read

This program uses BEGIN to print a heading before the file is read

gawk 'BEGIN { print "NAME\tRATE\tHOURS"; print ""}{ print }' emp.dat

(printf_BEGIN1.bash)

END

• The special pattern END matches after the last line of the last file has been processed

This program uses END to count the number of employees that have worked more than 15 hours

gawk '$3 > 15 { emp = emp + 1 } END { print emp, "employees worked more than 15 hours" }' emp.dat

(printf_END1.bash)

Computing Sums and Averages

• This program uses NR to compute average employee pay

gawk '{ pay = pay + $2 * $3 }
END { print NR, "employees"
printf( "total pay is $%7.2f\n", pay )
printf( "average pay is $%7.2f\n", pay/NR )}' emp.dat;

Question: What if NR == 0?

Handling Text

• This program finds which employee makes the most per hour

gawk '$2 > maxRate { maxRate = $2; maxEmp = $1 }
END { print "Highest hourly rate:", maxRate, "for", maxEmp )}' emp.dat;

(printf_END3.bash)

String Concatenation

• This program new strings by combining old ones

gawk '{ names = names $1 " " }
END { print names }' emp.dat;

(printf_END4.bash)

Printing the Last Input Line

• Although NR retains its value in an END action, $0 does not

• This program is one solution to the problem

gawk '{ last = $0 }
END { print last }' emp.dat;

(printf_END5.bash)