GREP_SED_AWK

grep, sed, awk, find чиать:
http://stackoverflow.com/questions/7727640/differences-among-grep-awk-and-sed
http://stackoverflow.com/questions/1632113/what-is-the-difference-between-sed-and-awk
http://unix.stackexchange.com/questions/132313/what-are-the-exact-differences-between-awk-and-cut-with-grep
https://davidlyness.com/post/the-functional-and-performance-differences-of-sed-awk-and-other-unix-parsing-utilities
http://matt.might.net/articles/sculpting-text/
https://wilsonericn.wordpress.com/2011/08/25/find-grep-sed-and-awk/