[: ==: 一元运算符预期-bash

[: ==: unary operator expected-bash

提问by user3493435

I am trying to read a text fiie sport.txt which contains the following and trying to match the user input with the sports name found in the text file,

我正在尝试读取包含以下内容的文本 fiie sport.txt 并尝试将用户输入与文本文件中找到的运动名称匹配，

if it's found it will print "sports found" and if it's not found it will print "No sports found"

如果找到它会打印“找到运动”，如果没有找到它会打印“没有找到运动”

the first example shown looks almost perfect till I tried to key in a random word and it displays an error
[: ==: unary operator expected

显示的第一个示例看起来几乎完美，直到我尝试输入一个随机单词并显示错误
[: ==: 一元运算符预期

I have also tried putting the "" for the variable in the second example shown but it will just print "No sports found" even though I typed a exact sports name matches with the sports name in the text file

我还尝试在显示的第二个示例中为变量添加“”，但它只会打印“未找到运动”，即使我在文本文件中键入了与运动名称匹配的确切运动名称

sports.txt

体育.txt

cycling
swimming 
batmintion

code( example 1 )

代码（示例1）

#!/bin/bash
file="sports.txt"
read -p "Enter a sports name": sportsName
existingSports=$(grep $sportsName $file);
if [ $existingSports == $sportsName ]; then
     echo "Sports Found"
else 
     echo "No Sports Found"
fi

if I key in 'swimming' base on the above codes

如果我根据上述代码输入“游泳”

output

输出

Sports Found

now if I key in 'swim'

现在如果我输入“游泳”

output

输出

No Sports Found

and if I key in a random word 'asd'

如果我输入一个随机单词“asd”

output

输出

[: ==: unary operator expected
No Sports Found

code( example 2 )

代码（示例2）

#!/bin/bash
file="sports.txt"
read -p "Enter a sports name": sportsName
existingSports=$(grep $sportsName $file);
if [ "$existingSports" == "$sportsName" ]; then
     echo "Sports Found"
else 
     echo "No Sports Found"
fi

if I key in 'swimming' base on the above codes

如果我根据上述代码输入“游泳”

output

输出

No Sports Found

now if I key in 'swim'

现在如果我输入“游泳”

output

输出

No Sports Found

code( example 3 )

代码（示例3）

#!/bin/bash
file="sports.txt"
read -p "Enter a sports name": sportsName
existingSports=$(grep $sportsName $file);
if [[ "$existingSports" == "$sportsName" ]]; then
     echo "Sports Found"
else 
     echo "No Sports Found"
fi

if I key in 'swimming' base on the above codes

如果我根据上述代码输入“游泳”

output

输出

No Sports Found

now if I key in 'swim'

现在如果我输入“游泳”

output

输出

No Sports Found

As mentioned the first example is almost close. what should I do to get rid of the error msg?

如上所述，第一个示例几乎接近。我应该怎么做才能摆脱错误消息？

采纳答案by anubhava

Instead of this block:

而不是这个块：

existingSports=$(grep $sportsName $file);
if [ $existingSports == $sportsName ]; then
     echo "Sports Found"
else 
     echo "No Sports Found"
fi

You can just utilize grep -qwith word boundariesand reduce your code to single line:

你可以只利用grep -q与字边界，减少您的代码一行：

grep -q "\<$sportsName\>" "$file" && echo "Sports Found" || echo "No Sports Found"

As per man grep:

根据man grep：

-q, --quiet, --silent

Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected.

-q, --quiet, --silent

Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected.

回答by Ashish

Try doing it in my way

尝试按照我的方式做

 #!/bin/bash
 file="sports.txt"
read -p "Enter a sports name": sportsName
 sportsName=`echo $sportsName | sed -e 's/^ *//g' -e 's/ *$//g'`
 #above sed command will remove all trailing and leading spaces which user can give as input
 result=`grep -c $sportsName $file`;
 if [ $result -eq 0 ]
  then
   echo "Sorry No match found"
  else

   echo "$result matches found"
 fi 

"-c" in grep will count number of occurrences and if occurrence is not 0 it shows the number of occurrences in else loop

grep 中的“-c”将计算出现次数，如果出现次数不为 0，则显示 else 循环中的出现次数

remember using "`" tild sign on grep command

记住在 grep 命令上使用“`”波浪号

If you are looking for exact word and not be be a substring of other word then use -w -c in grep command

如果您正在寻找确切的单词而不是其他单词的子字符串，请在 grep 命令中使用 -w -c

result=`grep -w -c $sportsName $file`;

man entries for -w

-w 的 man 条目

   -w, --word-regexp
      Select only those  lines  containing  matches  that  form  whole
      words.   The  test is that the matching substring must either be
      at the beginning of the line, or preceded  by  a  non-word  con-
      stituent  character.  Similarly, it must be either at the end of
      the line or followed by a non-word constituent character.  Word-
      constituent  characters are letters, digits, and the underscore.