awk notes

Awk is an excellent filter and report writer. Many UNIX utilities generates rows and columns of information. AWK is an excellent tool for processing these rows and columns, and is easier to use AWK than most conventional programming languages. AWK also has string manipulation functions, so it can search for particular strings and modify the output. AWK also has associative arrays, which are incredible useful, and is a feature most computing languages lack. Associative arrays can make a complex problem a trivial exercise.

I've frequently used awk with a variety UNIX commands to makelife easier for me, here are some one-liners that may prove helpfull.

Print column1, column5 and column7 of a data file or output of any columns list

awk '{print $1, $5, $7}' data_file

cat file_name |awk '{print $1 $5 $7}'

ls -al |awk '{print $1, $5, $7}' -- Prints file_permissions,size and date

List all files names whose file size greater than zero.

ls -al |awk '$5 > 0 {print $9}'

List all files whose file size equal to 512bytes.

ls -al |awk '$5 == 0 {print $9}'

print all lines

awk '{print }' file_name

awk '{print 0}' file_name

Number of lines in a file

awk ' END {print NR}' file_name

Number of columns in each row of a file

awk '{print NF}' file_name

Sort the output of file and eliminate duplicate rows

awk '{print $1, $5, $7}' |sort -u

List all file names whose file size is greater than 512bytes and owner is -oracle-

ls -al |awk '$3 == "oracle" && $5 > 512 {print $9}'

List all file names whose owner could be either -oracle- or -root-

ls -al |awk '$3 == "oracle" || $3 == "root" {print $9}'

list all the files whose owner is not -oracle

ls -al |awk '$3 != "oracle" {print $9}'

List all lines which has at least one or more characters

awk 'NF > 0 {print }' file_name

List all lines longer that 50 characters

awk 'length($0) > 50 {print }' file_name

List first two columns

awk '{print $1, $2}' file_name

Swap first two columns of a file and print

awk '{temp = $1; $1 = $2; $2 = temp; print }' file_name

Replace first column as -ORACLE- in a data file

awk '{$1 = "ORACLE"; print }' data_file

Remove first column values in a data file

awk '{$1 =""; print }' data_file

Calculate total size of a directory in Mb

ls -al |awk '{total +=$5};END {print "Total size: " total/1024/1024 " Mb"}'

Calculate total size of a directory including sub directories in Mb

ls -lR |awk '{total +=$5};END {print "Total size: " total/1024/1024 " Mb"}'

Find largest file in a directory including sub directories

ls -lR |awk '{print $5 "\t" $9}' |sort -n |tail -1

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