意外标记“then"附近的语法错误 [英] Syntax error near unexpected token 'then'

问题描述

我输入的代码与 Linux 命令行相同:完整介绍，第 369 页但是提示错误:

I typed the code the same as The Linux Command Line: A Complete Introduction, page 369 but prompt the error:

line 7 `if[ -e "$FILE" ]; then`

代码如下:

#!/bin/bash
#test file exists

FILE="1"
if[ -e "$FILE" ]; then
  if[ -f "$FILE" ]; then
     echo :"$FILE is a regular file"
  fi
  if[ -d "$FILE" ]; then
     echo "$FILE is a directory"
  fi
else 
   echo "$FILE does not exit"
   exit 1
fi
   exit

我想弄清楚是什么引入了错误.如何修改代码?我的系统是 Ubuntu.

I want to figure out what introduced the error. How can I modify the code? My system is Ubuntu.

推荐答案

if 和 [ 之间必须有一个空格，像这样:

There must be a space between if and [, like this:

#!/bin/bash
#test file exists

FILE="1"
if [ -e "$FILE" ]; then
  if [ -f "$FILE" ]; then
     echo :"$FILE is a regular file"
  fi
...

这些(以及它们的组合)也会不正确:

These (and their combinations) would all be incorrect too:

if [-e "$FILE" ]; then
if [ -e"$FILE" ]; then
if [ -e "$FILE"]; then

另一方面这些都可以:

if [ -e "$FILE" ];then  # no spaces around ;
if     [    -e   "$FILE"    ]   ;   then  # 1 or more spaces are ok

顺便说一句，这些是等价的:

Btw these are equivalent:

if [ -e "$FILE" ]; then
if test -e "$FILE"; then

这些也是等价的:

if [ -e "$FILE" ]; then echo exists; fi
[ -e "$FILE" ] && echo exists
test -e "$FILE" && echo exists

而且，使用这样的 elif 会更好地编写脚本的中间部分:

And, the middle part of your script would have been better with an elif like this:

if [ -f "$FILE" ]; then
    echo $FILE is a regular file
elif [ -d "$FILE" ]; then
    echo $FILE is a directory
fi

(我也去掉了 echo 中的引号，因为在这个例子中它们是不必要的)

(I also dropped the quotes in the echo, as in this example they are unnecessary)

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