如何在 tcsh if 语句中使用 OR 条件

Question

我试图在 tcsh shell 的 IF 语句中使用 OR 条件。相同的语句适用于 CSH。

示例语句：(cat tesh.sh)

if [ "$1" == "hi" -o "$2" == "hello" ];then
echo hi
else
echo hello
fi

现在，如果我执行这个示例脚本，我会收到以下错误：

[35] % sh -x test hi hi hello
+ test hi hi hello
test[7]: hi: A test command parameter is not valid.
+ exit 1
[36] % sh -x test hi hi
+ test hi hi
test[7]: test: Specify a parameter with this command.
+ exit 1
[37] % sh -x test hi hello
+ test hi hello
test[7]: test: Specify a parameter with this command.
+ exit 1
[38] % sh -x test hi hello
+ test hi hello
test[7]: test: Specify a parameter with this command.
+ exit 1
[39] %

请建议可以做什么？

附加信息：

[44] % uname -s
HP-UX
[45] %
[45] % echo $SHELL
/bin/tcsh
[46] %

更多示例：

 cat new_test.txt
if ([ $1 == 1 ] || [ $2 == 1 ])
then
echo $1 and $2
fi

./new_test.txt 1 1
./new_test.txt: ==: A test command parameter is not valid.
./new_test.txt: ==: A test command parameter is not valid.

更多示例：

 cat suggested.sh

if (($1 == 1) || ($2 == 1)) ; then echo "$1 and $2" ; fi

 ./suggested.sh 1 1
./suggested.sh: 1:  not found.
./suggested.sh: 1:  not found.

Answer 1

有一些困惑：

1. 您的第一个脚本是用 bourne-shell 编写的
2. 您的脚本没有提到应该使用什么 shell 来解释它（这可能会导致一些混淆，具体取决于您执行它的方式）
3. 您的第二个脚本是 tcsh 脚本，但具有误导性语法
4. 您似乎不知道[ 是什么。

像这样修改第一个脚本：

#!/bin/sh
if [ "$1" == "hi"  -o   "$2" == "hello" ]; then
  echo hi
else
  echo hello
fi

这意味着如果可执行此脚本将使用/bin/sh 来解释它。但是，如果你用命令强制 shell：

% sh -x test hi hi
+ '[' hi == hi -o hi == hello ']'
+ echo hi
hi
% tcsh -x test hi hi
if [ hi = hi -o hi = hello ]
if: Expression Syntax.
then
then: Command not found.
%

您可以观察到使用错误的 shell 会导致一些语法错误。

如果你想写一个 tcsh 脚本，这是一个解决方案：

#!/bin/tcsh
if ( "$1" == "hi"  ||  "$2" == "hello" ) then
  echo hi
else
  echo hello
endif

if 的语法不同，因为 tcsh 具有标准 bourne shell 所没有的内部测试功能。在 bourne 中，shell 测试是使用外部命令 test 进行的，该命令具有别名 [。所以你可以阅读手册中关于testsyntax 的文档：

SYNOPSIS
     test expression
     [ expression ] ...
     s1 = s2       True if the strings s1 and s2 are identical. ...
     expression1 -o expression2
                   True if either expression1 or expression2 are true.

对于 tcsh 的 if，请阅读 tcsh（或其父级 csh）的手册：

   if (expr) command
           If  expr (an expression, as described under Expressions) evalu-
           ates true, then command is executed.  Variable substitution  on
           command happens early, at the same time it does for the rest of
           the if command.  command must  be  a  simple  command,  not  an
           alias,  a  pipeline,  a command list or a parenthesized command
           list, but it  may  have  arguments.   Input/output  redirection
           occurs  even if expr is false and command is thus not executed;
           this is a bug.

   if (expr) then
   ...
   else if (expr2) then
   ...
   else
   ...
   endif   If the specified expr is true then the commands  to  the  first
           else are executed; otherwise if expr2 is true then the commands
           to the second else are executed, etc.  Any  number  of  else-if
           pairs are possible; only one endif is needed.  The else part is
           likewise optional.  (The words else and endif  must  appear  at
           the  beginning  of input lines; the if must appear alone on its
           input line or after an else.)

  Logical, arithmetical and comparison operators
       These operators are similar to those of C and have the same precedence.
       They include

           ||  &&  |  ^  &  ==  !=  =~  !~  <=  >=
           <  > <<  >>  +  -  *  /  %  !  ~  (  )
...