Hartigan/Computer/AWK

Hartigan/Computer/AWK
EXAMPLES # is the comment character for awk. 'field' means 'column'

# Print first two fields in opposite order:
awk '{ print $2, $1 }' file

# Print lines longer than 72 characters:
awk 'length > 72' file

# Print length of string in 2nd column
awk '{print length($2)}' file

# Add up first column, print sum and average:
{ s += $1 }
END { print "sum is", s, " average is", s/NR }

# Print fields in reverse order:
awk '{ for (i = NF; i > 0; --i) print $i }' file

# Print the last line
{line = $0}
END {print line}

# Print the total number of lines that contain the word Pat
/Pat/ {nlines = nlines 1}
END {print nlines}

# Print all lines between start/stop pairs:
awk '/start/, /stop/' file

# Print all lines whose first field is different from previous one:
awk '$1 != prev { print; prev = $1 }' file

# Print column 3 if column 1 > column 2:
awk '$1 > $2 {print $3}' file

# Print line if column 3 > column 2:
awk '$3 > $2' file

# Count number of lines where col 3 > col 1
awk '$3 > $1 {print i "1"; i }' file

# Print sequence number and then column 1 of file:
awk '{print NR, $1}' file

# Print every line after erasing the 2nd field
awk '{$2 = ""; print}' file

# Print hi 28 times
yes | head -28 | awk '{ print "hi" }'

# Print hi.0010 to hi.0099 (NOTE IRAF USERS!)
yes | head -90 | awk '{printf("hi00%2.0f n", NR 9)}'

# Replace every field by its absolute value
{ for (i = 1; i < = NF; i=i 1) if ($i < 0) $i = -$i print} # If you have another character that delimits fields, use the -F option # For example, to print out the phone number for Jones in the following file, # 000902|Beavis|Theodore|333-242-2222|149092 # 000901|Jones|Bill|532-382-0342|234023 # ... # type awk -F"|" '$2=="Jones"{print $4}' filename # Some looping for printouts BEGIN{ for (i=875;i>833;i--){
printf "lprm -Plw %dn", i
} exit
}

Formatted printouts are of the form printf( "formatn", value1, value2, ... valueN)
e.g. printf("howdy %-8s What it is bro. %.2fn", $1, $2*$3)
%s = string
%-8s = 8 character string left justified
%.2f = number with 2 places after .
%6.2f = field 6 chars with 2 chars after .
n is newline
t is a tab

# Print frequency histogram of column of numbers
$2 < = 0.1 {na=na 1} ($2 > 0.1) && ($2 < = 0.2) {nb = nb 1} ($2 > 0.2) && ($2 < = 0.3) {nc = nc 1} ($2 > 0.3) && ($2 < = 0.4) {nd = nd 1} ($2 > 0.4) && ($2 < = 0.5) {ne = ne 1} ($2 > 0.5) && ($2 < = 0.6) {nf = nf 1} ($2 > 0.6) && ($2 < = 0.7) {ng = ng 1} ($2 > 0.7) && ($2 < = 0.8) {nh = nh 1} ($2 > 0.8) && ($2 < = 0.9) {ni = ni 1} ($2 > 0.9) {nj = nj 1}
END {print na, nb, nc, nd, ne, nf, ng, nh, ni, nj, NR}

# Find maximum and minimum values present in column 1
NR == 1 {m=$1 ; p=$1}
$1 >= m {m = $1}
$1 < = p {p = $1} END { print "Max = " m, " Min = " p } # Example of defining variables, multiple commands on one line NR == 1 {prev=$4; preva = $1; prevb = $2; n=0; sum=0} $4 != prev {print preva, prevb, prev, sum/n; n=0; sum=0; prev = $4; preva = $1; prevb = $2} $4 == prev {n ; sum=sum $5/$6} END {print preva, prevb, prev, sum/n} # Example of using substrings # substr($2,9,7) picks out characters 9 thru 15 of column 2 {print "imarith", substr($2,1,7) " - " $3, "out."substr($2,5,3)} {print "imarith", substr($2,9,7) " - " $3, "out."substr($2,13,3)} {print "imarith", substr($2,17,7) " - " $3, "out."substr($2,21,3)} {print "imarith", substr($2,25,7) " - " $3, "out."substr($2,29,3)}

One Reply to “Hartigan/Computer/AWK”

  1. # Add up first column, print sum and average:
    { s = $1 }
    END { print “sum is”, s, ” average is”, s/NR }

    This missing a “plus”
    # Add up first column, print sum and average:
    { s += $1 }
    END { print “sum is”, s, ” average is”, s/NR }

    will return the sum

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