text edit,

目录

• top
• sort
• uniq
• cut
• sed command
  • add
  • delete
• shell script basics
• type used to check [[
• single and double bracket

top

Values under 1.0 indicate that the machine is not busy.
/proc/cpuinfo

sort

cat -e test.sh
print no display word
-n display blank line

sort by multiple column
sort -k 1,1 -k 2n distros.txt

sort -k 3.7 nbr -k3.1nbr distros.txt

sort default with tabs and spaces
可以指定 by -t
sort -t “:” -k 7 /etc/passwd

uniq

sort foo.txt |uniq -c

cut

cat xxx.txt|head -2|cut -d' ' -f 1-3

https://blog.csdn.net/wuli13141516/article/details/104419255

sed command

echo “front”| sed “s_front_back”

add

插入

sed -i "2a iii" test.txt
sed -i '2a append' test.txt

mac default has backup , skip backup by add one more parameter

sed -i "" "2a iii" test.txt
sed -i "" '2a append' test.txt

delete

sed -i '2d' test.txt

shell script basics

思考如何弄test 即 if 语句

• $0 script name
  $# script parameter numbers
  $@ all parameters
  $? scrip return

type used to check [[

https://www.baeldung.com/linux/bash-single-vs-double-brackets

single and double bracket

The single bracket is a built-in command that’s older than the double bracket. The double bracket is an enhanced version of the single bracket. If we want the portability of scripts, we should prefer single brackets. However, using the double brackets is generally more convenient.