AWK Features:1. Field/Column processor 2. Supports egrep-compatible (POSIX) RegExes 3. Can return full lines like grep 4. Awk runs 3 steps: a. BEGIN - optional b. Body, where the main action(s) take place c. END - optional 5. Multiple body actions can be executed by separating them using semicolons. e.g. '{ print $1; print $2 }' 6. Awk, auto-loops through input stream, regardless of the source of the stream. e.g. STDIN, Pipe, File Usage: 1. awk '/optional_match/ { action }' file_name | Pipe 2. awk '{ print $1 }' grep1.txt Note: Use single quotes with awk, to avoid shell interpolation of awk's variables 3. awk '{ print $1,$2 }' grep1.txt Note: Default input and output field separators is whitespace 4. awk '/linux/ { print } ' grep1.txt - this will print ALL lines containing 'linux' 5. awk '{ if ($2 ~ /Linux/) print}' grep1.txt 6. awk '{ if ($2 ~ /8/) print }' /var/log/messages - this will print the entire line for log items for the 8th 7. awk '{ print $3 }' /var/log/messages | awk -F: '{ print $1}' Sed - Stream Editor:
Features:
1. Faciliates automated text editing 2. Supports RegExes (POSIX) 3. Like Awk, supports scripting using '-F' option 4. Supports input via: STDIN, pipe, file Usage: 1. sed [options] 'instruction[s]' file[s] 2. sed -n '1p' grep1.txt - prints the first line of the file 3. sed -n '1,5p' grep1.txt - prints the first 5 lines of the file 4. sed -n '$p' grep1.txt - prints the last line of the file 5. sed -n '1,3!p' grep1.txt - prints ALL but lines 1-3 6. sed -n '/linux/p' grep1.txt - prints lines with 'linux' 7. sed -e '/^$/d' grep1.txt - deletes blank lines from the document 8. sed -e '/^$/d' grep1.txt > sed1.txt - deletes blank lines from the document 'grep1.txt' and creates 'sed1.txt' 9. sed -ne 's/search/replace/p' sed1.txt 10. sed -ne 's/linux/unix/p' sed1.txt 11. sed -i.bak -e 's/3/4' sed1.txt - this backs up the original file and creates a new 'sed1.txt' with the modifications indicated in the command Note: Generally, to create new files, use output redirection, instead of allowing sed to write to STDOUT Note: Sed applies each instruction to each line
