linux - bash 中的错误 - 预期存在 -e 的一元运算符

Question

在我使用“read”创建它之后，我想测试两个变量是否存在。如果用户只输入我想要的两个变量之一，它会显示错误。

这是我的代码:

while true;
do
  echo "Saisissez deux variables x et y sous la forme [x y]"
  read x y

  if [ !-e $x ] || [ !-e $y ] <<<<<< problem ligne
  then
    echo "Vous devez renseigner deux nombres x et y"
  elif [ $x = "." ]
  then
    exit 0
  else
    calcul $x $y
  fi
done

当我输入参数时出现错误:

[: !-e: unary operator expected

感谢您的帮助:)

Answer 1

将其更改为:

if [ -z "$x" ] || [ -z "$y" ]

解释

• [ 实际上是一个内置的 shell(在提示符下尝试 which [ 或 help [)；它是 test 的同义词。
• -z 是 [ 的参数。它的意思是“测试下一个字符串的长度是否为 0；如果是则返回 true；否则返回 false。
• 始终用双引号将您正在测试的变量括起来!

这是 [ 的有用选项列表，因为我认为您会感兴趣:

-b file = True if the file exists and is block special file. 
-c file = True if the file exists and is character special file. 
-d file = True if the file exists and is a directory. 
-e file = True if the file exists. 
-f file = True if the file exists and is a regular file 
-g file = True if the file exists and the set-group-id bit is set. 
-k file = True if the files "sticky" bit is set. 
-L file = True if the file exists and is a symbolic link. 
-p file = True if the file exists and is a named pipe. 
-r file = True if the file exists and is readable. 
-s file = True if the file exists and its size is greater than zero. 
-s file = True if the file exists and is a socket. 
-t fd = True if the file descriptor is opened on a terminal. 
-u file = True if the file exists and its set-user-id bit is set. 
-w file = True if the file exists and is writable. 
-x file = True if the file exists and is executable. 
-O file = True if the file exists and is owned by the effective user id. 
-G file = True if the file exists and is owned by the effective group id. 
file1 –nt file2 = True if file1 is newer, by modification date, than file2. 
file1 ot file2 = True if file1 is older than file2. 
file1 ef file2 = True if file1 and file2 have the same device and inode numbers. 
-z string = True if the length of the string is 0. 
-n string = True if the length of the string is non-zero. 
string1 = string2 = True if the strings are equal. 
string1 != string2 = True if the strings are not equal. 
!expr = True if the expr evaluates to false. 
expr1 –a expr2 = True if both expr1 and expr2 are true. 
expr1 –o expr2 = True is either expr1 or expr2 is true.