# cat example.txt | awk 'NR%2==1'
remove all even lines from example.txt [man]
# echo a b c | awk '{print $1}'view the first column of a line [man]
# echo a b c | awk '{print $1,$3}'view the first and third column of a line [man]
# cat -n file1
number row of a file [man]
# comm -1 file1 file2
compare contents of two files by deleting only unique lines from 'file1' [man]
# comm -2 file1 file2
compare contents of two files by deleting only unique lines from 'file2' [man]
# comm -3 file1 file2
compare contents of two files by deleting only the lines that appear on both files [man]
# diff file1 file2
find differences between two files [man]
# grep Aug /var/log/messages
look up words "Aug" on file '/var/log/messages' [man]
# grep ^Aug /var/log/messages
look up words that begin with "Aug" on file '/var/log/messages' [man]
# grep [0-9] /var/log/messages
select from file '/var/log/messages' all lines that contain numbers [man]
# grep Aug -R /var/log/*
search string "Aug" at directory '/var/log' and below [man]
# paste file1 file2
merging contents of two files for columns [man]
# paste -d '+' file1 file2
merging contents of two files for columns with '+' delimiter on the center [man]
# sdiff file1 file2
find differences between two files and merge interactively alike "diff" [man]
# sed 's/string1/string2/g' example.txt
replace "string1" with "string2" in example.txt [man]
# sed '/^$/d' example.txt
remove all blank lines from example.txt [man]
# sed '/ *#/d; /^$/d' example.txt
remove comments and blank lines from example.txt [man]
# sed -e '1d' exampe.txt
eliminates the first line from file example.txt [man]
# sed -n '/string1/p'
view only lines that contain the word "string1" [man]
# sed -e 's/ *$//' example.txt
remove empty characters at the end of each row [man]
# sed -e 's/string1//g' example.txt
remove only the word "string1" from text and leave intact all [man]
# sed -n '1,5p' example.txt
print from 1th to 5th row of example.txt [man]
# sed -n '5p;5q' example.txt
print row number 5 of example.txt [man]
# sed -e 's/00*/0/g' example.txt
replace more zeros with a single zero [man]
# sort file1 file2
sort contents of two files [man]
# sort file1 file2 | uniq
sort contents of two files omitting lines repeated [man]
# sort file1 file2 | uniq -u
sort contents of two files by viewing only unique line [man]
# sort file1 file2 | uniq -d
sort contents of two files by viewing only duplicate line [man]
# echo 'word' | tr '[:lower:]' '[:upper:]'
convert from lower case in upper case [man]