I am new to Shell Scripts and not aware of the syntax.
我有一个 shell 脚本,我正在推送到我的安卓设备,然后用"busybox dos2unix"转换它:
adb shell busybox dos2unix /data/local/myShellScript.sh
在脚本中,我正在尝试检查字符串是否为空?但是我收到错误:"意外的运算符/操作数"。
以下是我的代码:
echo "Getting a PID (Process ID) from a file" ;
pid=`cat /sdcard/PIDofTask.txt` ;
echo "PID of task is : " $pid ;
echo "Checking if the pid exists, to verify the process is running" ;
pidString=$(ps | grep ${pid}) ;
echo "PID string : " $pidString ;
if [ $pidString ] ;
then
echo "pid String is not empty" ;
else
echo "pid String is empty" ;
fi ;
输出:
Getting a PID (Process ID) from a file
PID of task is : 11571
Checking if the pid exists, to verify the process is running
PID string : root 11571 8082 4180 1828 poll_sched 7faa42dcdc S sh
/data/local/myShellScript.sh[2]: [: 11571: unexpected operator/operand
pid String is empty
我也尝试了 [ -n $pidString ] 和 [ -z $pidString ] 选项。但两者都给出了错误。
我哪里做错了?非常感谢帮助...
检查空字符串。
例:
line="hello welcome"
if [ -z "$line" ] ; then
echo "String null"
fi
要检查空字符串,您需要使用 -z。
例:
if [ -z "$str" ] ;