Shell10 good habits

MichaelStutz, author of TheLinuxCookbook, summed up 10 good habits based on years of UNIX experience. I personally think it is really useful. The following is a summary of this article. 1. create a hierarchical Directory: Use the-p option of mkdir, for example, mkdir-ptmp/a/B/c2. unpackage to the specified directory: Use the tar-cstrap, for example, tarxvfnewarc.tar. michael Stutz, author of The Linux Cookbook, has summed up 10 good habits based on his years of UNIX experience. I personally think it is really useful. The following is a summary of this article.



1. Create a hierarchical Directory: Use the-p option of mkdir, such as mkdir-p tmp/a/B/c.


2. Unpack to the specified directory: Use the-C option of tar, such as tar xvf newarc.tar.gz-C tmp/a/B/c




3. Combined commands: Use;, &, |, and other control operators, such as cd tmp/a/B/c & tar xvf ~ /Archive.tar

4. Use variables with caution: place the variables in "", as shown in figure

~ $ ls tmp/  a b  ~ $ VAR="tmp/*"  ~ $ echo $VAR  tmp/a tmp/b  ~ $ echo "$VAR"  tmp/*  ~ $ echo $VARa   ~ $ echo "$VARa"    ~ $ echo "${VAR}a"  tmp/*a  ~ $ echo ${VAR}a  tmp/a  ~ $ 

5. Long command input: broken by \ branch, as shown in figure

~ $ cd tmp/a/b/c || \  > mkdir -p tmp/a/b/c && \  > tar xvf -C tmp/a/b/c ~/archive.tar  

6. Group commands: Use () and {} to group commands, as shown in figure

~ $ ( cd tmp/a/b/c/ || mkdir -p tmp/a/b/c && \  > VAR=$PWD; cd ~; tar xvf -C $VAR archive.tar ) \  > | mailx admin -S "Archive contents"  

7. Use xargs to filter the output, as shown in figure

~/tmp $ ls -l | xargs  -rw-r--r-- 7 joe joe 12043 Jan 27 20:36 December_Report.pdf -rw-r--r-- 1 \  root root 238 Dec 03 08:19 README drwxr-xr-x 38 joe joe 354082 Nov 02 \  16:07 a -rw-r--r-- 3 joe joe 5096 Dec 14 14:26 archive.tar -rwxr-xr-x 1 \  joe joe 3239 Sep 30 12:40 mkdirhier.sh  ~/tmp $ 

8. You can use the-c option of grep to calculate the number of output rows, which is faster than the wc-l of the pipeline, as shown in

  ~ $ time grep and tmp/a/longfile.txt | wc -l    2811     real 0m0.097s    user 0m0.006s    sys 0m0.032s    ~ $ time grep -c and tmp/a/longfile.txt    2811        real 0m0.013s    user 0m0.006s  sys 0m0.005s  ~ $  

9. Match the output field: Use awk, as shown in figure

1. ~ /Tmp $ ls-l | awk '$6 = "Dec "'
2. -Rw-r -- 3 joe 5096 Dec 14 archive.tar
3. -Rw-r -- 1 root 238 Dec 03 08:19 README
4. ~ /Tmp $

10. Disable cat pipeline output: it can be replaced by grep, as shown in figure

~ $ time cat tmp/a/longfile.txt | grep and   2811    real 0m0.015s   user 0m0.003s   sys 0m0.013s   ~ $ time grep and tmp/a/longfile.txt   2811   real 0m0.010s   user 0m0.006s   sys 0m0.004s   ~ $