The simplest shell script

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The following code is the simplest Shell script , TA will show you Shell script Charm!

 <trans data-src="#!/">#!/</trans> <trans data-src="bin/bash">bin/bash</trans> <trans data-src="#Empty file content  BY:byrd">#Empty file content  BY:byrd</trans> <trans data-src="LOG_DIR=/tmp/log    #定义变量">LOG_DIR=/tmp/log # Define variables</trans> <trans data-src="ROOT_UID=0    #同上">ROOT_UID=0 # Same as above</trans> <trans data-src="if [ "$UID" -ne "$ROOT_UID" ]    #检测用户uid是否是0，如果是脚本继续执行，如果不是，则退出，且返回echo语句">If ["$UID" - ne "$ROOT_UID"] # Check whether the user uid is 0. If the script continues to execute, if not, exit and return the echo statement</trans> <trans data-src="then">then</trans> <trans data-src="echo "Must be root to run this script.">echo "Must be root to run this script.</trans> <trans data-src=""">"</trans> <trans data-src="exit 1">exit 1</trans> <trans data-src="fi">fi</trans> <trans data-src="cd $LOG_DIR ||     #进入/tmp/log目录，如果没有则提示没有此目录，若存在脚本继续">Cd $LOG_DIR | | # Enter the/tmp/log directory. If not, you will be prompted that there is no such directory. If there is a script, continue</trans> <trans data-src="{">{</trans> <trans data-src="echo "Can not change to necessary directory.">echo "Can not change to necessary directory.</trans> <trans data-src="" >&2">" >&2</trans> <trans data-src="exit 1">exit 1</trans> <trans data-src="}">}</trans> <trans data-src="if [ -f "messages" ];    #">if [ -f "messages" ];    #</trans> <trans data-src="在/tmp/log目录中如果存在messages则清空，如果没有文件则推出。">If there are messages in the/tmp/log directory, it will be cleared. If there are no files, it will be pushed out.</trans> <trans data-src="then">then</trans> <trans data-src="cat /dev/null >messages && echo "Logs cleaned up.">cat /dev/null >messages && echo "Logs cleaned up.</trans> <trans data-src=""">"</trans> <trans data-src="exit 0">exit 0</trans> <trans data-src="else">else</trans> <trans data-src="echo "Can not find this file.">echo "Can not find this file.</trans> <trans data-src=""">"</trans> <trans data-src="exit 1">exit 1</trans> <trans data-src="fi">fi</trans>

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#!/ bin/bash

#Empty file content BY:byrd

LOG_DIR =/ tmp / log #Define variables

ROOT_UID = zero #Same as above

if [ "$UID" - ne "$ROOT_UID" ] #Check whether the user uid is 0. If the script continues to execute, if not, exit and return the echo statement

then

echo "Must be root to run this script."

exit one

cd $ LOG_DIR | | #Enter the/tmp/log directory. If not, you will be prompted that there is no such directory. If there is a script, continue

{

echo "Can not change to necessary directory." > &2

exit 1

}

if [ -f "messages" ]; #If there are messages in the/tmp/log directory, it will be cleared. If there are no files, it will be pushed out.

then

cat / dev / null > messages && echo "Logs cleaned up."

exit zero

else

echo "Can not find this file."

exit one

Statement: This article is original by BYRD (based on GNU bash, version 4.1.2), and reprinting without permission is prohibited! SourceByrd's Weblog- https://note.t4x.org/code/empty-file-content/

Statement: unless otherwise specified Byrd's Blog The content is original. Reproduction without permission is prohibited! For details, please read Copyright Statement !

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