Using Linux for so long, these tips you may not know yet!

We shared 30 Linux usage tips last week, but not enough! Today summed up some, on the road to learning Linux hope to help you.
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31, the Monitoring directory, the newly created file name is appended to the log

#要安装inotify-tools软件包#!/bin/bashMON_DIR=/optinotifywait -mq --format %f -e create $MON_DIR |while read files; do  echo $files >> test.logdone

32. Find multiple specified file types at once

# find ./ -name ‘*.jpg‘ -o -name ‘*.png‘# find ./ -regex ".*\.jpg\|.*\.png"

33. String splitting

# echo "hello" |awk -F ‘‘ ‘{for(i=1;i<=NF;i++)print $i}‘# echo "hello" |sed ‘s/./&\n/g‘# echo "hello" |sed -r ‘s/(.)/\1\n/g‘

34, real-time monitoring command operation results

# watch -d -n 1 ‘ifconfig‘

35, solve the message garbled problem

# echo `echo "content" | iconv -f utf8 -t gbk` | mail -s "`echo "title" | iconv -f utf8 -t gbk`" [email protected]注：通过iconv工具将内容字符集转换

36. Add a newline or content in the text every three lines

# sed ‘4~3s/^/\n/‘ file# awk ‘$0;NR%3==0{print "\n"}‘ file# awk ‘{print NR%3?$0:$0 "\n"}‘ file

37. Delete the matching line and the last line or the previous line

# sed ‘/abc/,+1d‘ file  #删除匹配行及后一行# sed ‘/abc/{n;d}‘ file #删除后一行# tac file |sed ‘/abc/,+1d‘ |tac  #删除前一行

38, statistics total number of rows

效率1 # wc -l file  效率2 # grep -c . file效率3 # awk ‘END{print NR}‘ file效率4 # sed -n ‘$=‘ file

39. Remove text opening and closing spaces

# sed -i ‘s/^[ \t]*//;s/[ \t]*$//‘ file

40. Add single quotation marks to a single IP

41. Print wait time in script

wait(){echo -n "wait 3s"for ((i=1;i<=3;i++)); do    echo -n "."    sleep 1doneecho }wait

42. Delete the specified line

# awk ‘NR==1{next}{print $0}‘ file #$0可省略# awk ‘NR!=1{print}‘ file# awk ‘NR!=1{print $0}‘ 或删除匹配行：awk ‘!/test/{print $0}‘# sed ‘1d‘ file# sed -n ‘1!p‘ file

43. Add a line before and after the specified line

在第二行前一行加txt：# awk ‘NR==2{sub(‘/.*/‘,"txt\n&")}{print}‘ a.txt # sed‘2s/.*/txt\n&/‘ a.txt在第二行后一行加txt：# awk ‘NR==2{sub(‘/.*/‘,"&\ntxt")}{print}‘ a.txt# sed‘2s/.*/&\ntxt/‘ a.txt

44. Get the NIC name via IP

# ifconfig |awk -F‘[: ]‘ ‘/^eth/{nic=$1}/192.168.18.15/{print nic}‘

45. Floating-point arithmetic (number 46 keeps the decimal point)

# awk ‘BEGIN{print 46/100}‘  0.46# echo 46|awk ‘{print $0/100}‘0.46# awk ‘BEGIN{printf "%.2f\n",46/100}‘0.46# echo ‘scale=2;46/100‘ |bc|sed ‘s/^/0/‘0.46# printf "%.2f\n" $(echo "scale=2;46/100" |bc)0.46

46. Floating-point comparison

方法1：if [ $(echo "4>3"|bc) -eq 1 ]; then    echo yeselse    echo nofi方法2：if [ $(awk ‘BEGIN{if(4>3)print 1;else print 0}‘) -eq 1 ]; then    echo yeselse    echo nofi

47. Replace the newline character with a comma

$ cat a.txt1:23替换后：1,2,3方法1：$ tr ‘\n‘ ‘,‘ < a.txt$ sed ‘:a;N;s/\n/,/;$!b a‘ a.txt$ sed ‘:a;$!N;s/\n/,/;t a‘ a.txt  :方法2：while read line; do    a+=($line)done < a.txtecho ${a[*]} |sed ‘s/ /,/g‘方法3：awk ‘{s=(s?s","$0:$0)}END{print s}‘ a.txt#三目运算符(a?b:c)，第一个s是变量，s?s","$0:$0,第一次处理1时，s变量没有赋值为假，结果打印1，第二次处理2时，s值是1，为真，结果1,2。以此类推，小括号可以不写。awk ‘{if($0!=3)printf "%s,",$0;else print $0}‘ a.txt

48, Windows under the text to Linux hidden format removal

方法1：打开文件后输入:set fileformat=unix方法2：打开文件后输入:%s/\r*$//  #^M可用\r代替方法3：sed -i ‘s/^M//g‘ a.txt  #^M的输入方式是ctrl+v,然后ctrl+m方法4：dos2unix a.txt

49, Xargs skillfully use

xargs -n1  #将单个字段作为一行# cat a.txt1 2 3 4# xargs -n1 < a.txt1234

xargs -n2 #将两个字段作为一行$ cat b.txtstringnumbera1b2$ xargs -n2 < a.txt string numbera 1b 2

50. Statistics the total size of files in the current directory ending in. html

方法1：# find . -name "*.html" -maxdepth 1 -exec du -b {} \; |awk ‘{sum+=$1}END{print sum}‘方法2：for size in $(ls -l *.html |awk ‘{print $5}‘); do    sum=$(($sum+$size))doneecho $sum递归统计：# find . -name "*.html" -exec du -k {} \; |awk ‘{sum+=$1}END{print sum}‘

Using Linux for so long, these tips you may not know yet!