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为什么这个脚本不起作用？

tag-icon • tag-icon linux shell
为什么这个脚本不起作用？ 
#!/bin/bash
if [ $# !=1 ]
then
   echo Usage: A single argument which is the directory to backup
   exit
fi
if [ ! -d ~/projects/$1 ]
then
   echo 'The given directory does not seem to exist (possible typo)'
   exit
fi
date=`date +%F`
if [ -d ~/projectbackups/$1_date ]
then
  echo 'this project has been backed up today, overwrite?'
  read answer
  if [ $answer != 'y' ]
  then
    exit
  fi
else
  mkdir ~/projectbackups/$1_$date
fi
cp -R ~/projects/$1 ~/projectbackups/$1_$date
echo Backup of $1 completed

我在项目文件夹下创建了子文件夹结果，如下所示：

[root@ip-10-0-7-125 result]# pwd
/root/projects/result

但是执行脚本的时候总是报错：

[root@ip-10-0-7-125 bash-tut]# ./pj-backup.sh /root/projects/result/
./pj-backup.sh: line 2: [: 1: unary operator expected
The given directory does not seem to exist (possible typo)
[root@ip-10-0-7-125 bash-tut]# ./pj-backup.sh resutl
./pj-backup.sh: line 2: [: 1: unary operator expected
The given directory does not seem to exist (possible typo)

你们能帮我解决这个问题吗？

答案1

!=在第 2 行，您错过了条件运算符和参数 ( )之间的空格1：

[ $# != 1 ]

例子：

$ set -- foo bar

$ [ $# !=1 ] && echo "OK"
bash: [: 2: unary operator expected

$ [ $# != 1 ] && echo "OK"
OK

$#此外，您还必须进行字符串比较，这在许多此类情况下可能会失败，例如，如果（将其替换为其他变量）的输出被设计为显示01为而不是1.因此，在进行算术比较时，请使用算术比较运算符，-ne在本例中：

[ $# -ne 1 ]

或者

(( $# != 1 ))

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