最近在使用linux的awk命令，感叹其强大之处，在文本操作上的便利支持，让在对数百万流水明细操作如鱼得水，
先贴出来awk的man，接下来再细致记录常用命令。
awk --help > awk.txt
===================================================awk.txt=======================================================
Usage: awk [POSIX or GNU style options] -f progfile [--] file ...
Usage: awk [POSIX or GNU style options] [--] 'program' file ...
POSIX options: GNU long options:
-f progfile --file=progfile
-F fs --field-separator=fs
-v var=val --assign=var=val
-m[fr] val
-O --optimize
-W compat --compat
-W copyleft --copyleft
-W copyright --copyright
-W dump-variables[=file] --dump-variables[=file]
-W exec=file --exec=file
-W gen-po --gen-po
-W help --help
-W lint[=fatal] --lint[=fatal]
-W lint-old --lint-old
-W non-decimal-data --non-decimal-data
-W profile[=file] --profile[=file]
-W posix --posix
-W re-interval --re-interval
-W source=program-text --source=program-text
-W traditional --traditional
-W usage --usage
-W use-lc-numeric --use-lc-numeric
-W version --version
To report bugs, see node `Bugs' in `gawk.info', which is
section `Reporting Problems and Bugs' in the printed version.
gawk is a pattern scanning and processing language.
By default it reads standard input and writes standard output.
Examples:
gawk '{ sum += $1 }; END { print sum }' file
gawk -F: '{ print $1 }' /etc/passwd