유용한 명령어

alias : 명령어를 간단하게 줄여사용

ex) alias ll='ls -alrt'

unalias: alias 삭제

* '\'를 붙여 사용하거나 명령어의 절대경로를 사용하여 명령어 입력하면 alias무시됨

apropos : 명령어 검색

* man -k 와 동일

arch : cpu 타입조회

arp : 연결시스템 mac주소 확인

at : 명령어 또는 스크립트 실행 예약

awk : 패턴검색

ex) awk /mail/ /etc/passwd -> passwd파일에서 'mail'이 포함된 라인을 출력

awk -F: /mail/'{print $1}' /etc/passwd -> 'mail'이 포함된 라인중 ':'을 구분자로 첫번째 토큰 출력

awk시스템변수

$0	refers to the entire line
$n	The fields are denoted $1, $2, ...
CONVFMT	conversion format used when converting numbers (default %.6g)
FS	regular expression used to separate fields; also settable by option -Ffs.
NF	number of fields in the current record
NR	ordinal number of the current record
FILENAME	the name of the current input file
RS	input record separator (default newline)
OFS	output field separator (default blank)
ORS	output record separator (default newline)
OFMT	output format for numbers (default %.6g)
SUBSEP	separates multiple subscripts (default 034)
ARGC	argument count, assignable
ARGV	argument array, assignable; non-null members are taken as filenames
ENVIRON	array of environment variables; subscripts are names
FNR	ordinal number of the current record in the current file

ex) awk /mail/'{print NR,$0, NF}' /etc/passwd

awk 함수

The mathematical functions exp, log, sqrt, sin, cos, and atan2 are built in

length / rand / srand / int / substr(d,m,n) / index(s,t) / match(s,r) /

split(s,a,fs) / sub(r,t,s) / gsub / sprintf(fmt,expr,...) / system(cmd) /

tolower(str) / toupper(str)

ex)

length($0) > 72
Print lines longer than 72 characters.

{ print $2, $1 }
Print first two fields in opposite order.

       BEGIN { FS = ",[ \t]*|[ \t]+" }
             { print $2, $1 }
              Same, with input fields separated by comma and/or blanks and tabs.

            { s += $1 }
       END { print "sum is", s, " average is", s/NR }
              Add up first column, print sum and average.

/start/, /stop/
Print all lines between start/stop pairs.

       BEGIN     {    # Simulate echo(1)
            for (i = 1; i < ARGC; i++) printf "%s ", ARGV[i]
            printf "\n"
            exit }

icocoa