Question

我正在尝试创建一个命令，列出目录中每个文件的第一行或最后一行（用户指定的编号），该文件也由用户指定。他们也可以选择使用头部或尾部。

HEADORTAIL=$1

NUMLINES=$2

DIRECTORY=$3

if [ $# -lt 3 ]
then
      echo "The command needs three arguments to work"
      echo "The usage of this command is as follows: lshead [-head or -tail] [n$
      exit
elif [ -d "$DIRECTORY" ]
then
    echo "This directory exists"
    while [ $2 -lt 1 ] ; do
            echo "The number of lines you wish to see must be greater than 0"
            read $2
    done
if [ $1 == "-head" ]
then
    head -$2 $HOME/$3/*
elif [ $1 == "-tail" ]
then
    tail -$2 $HOME/$3/*
    exit
fi
fi
fi
fi
exit

我真的不知道从终端的答案会有什么期待。如果我犯了任何错误或做了任何愚蠢的事，我会道歉。我相对知道打击shell脚本和本网站。

运行命令时出现此错误。

lshead3 -head 10 bin
./lshead3: line 30: syntax error near unexpected token `fi'
./lshead3: line 30: `fi'

当我把它放入ShellCheck

时就得到了这个

$ shellcheck myscript

    Line 9:
        echo "The usage of this command is as follows: lshead [-head or -tail] [n$
        ^-- SC1009: The mentioned parser error was in this simple command.
             ^-- SC1078: Did you forget to close this double quoted string?

    Line 11:
    elif [ -d "$DIRECTORY" ]
          ^-- SC1079: This is actually an end quote, but due to next char it looks suspect.
                     ^-- SC1078: Did you forget to close this double quoted string?

    Line 13:
        echo "This directory exists"
             ^-- SC1079: This is actually an end quote, but due to next char it looks suspect.

    Line 21:
    elif [ $1 == "-tail" ]
                   ^-- SC1073: Couldn't parse this double quoted string.

    Line 28:

^-- SC1072: Expected end of double quoted string. Fix any mentioned problems and try again.

$

Answer 1

  1 #!/bin/bash

  2 head_or_tail=$1
  3 num_lines=$2
  4 directory=$3
  5
  6 if [ $# -ne 3 ]
  7 then
  8     echo "The command needs three arguments to work"
  9     echo "The usage of this command is as follows: lshead [head or tail] [numlines] [directory]"
 10     exit 1
 11 fi
 12
 13
 14 if [[ "$num_lines" -lt 1 ]]
 15 then
 16     echo "The number of lines you wish to see must be greater than 0"
 17     exit 1
 18 fi
 19
 20 if [[ ! -d "$directory" ]]
 21 then
 22     echo "Directory $directory does not exist"
 23     exit 1
 24 else
 25     echo "looking in directoy $directory"
 26     if [[ "$head_or_tail" = "head" ]]
 27     then
 28         head -n "$num_lines" "$directory"/*
 29     elif [[ "$head_or_tail" = "tail" ]]
 30     then
 31         tail -n "$num_lines" "$directory"/*
 32     fi
 33 fi
 34 exit

注：

第2-4行：将命令行参数存储到变量中，以便向下使用它们，并保持代码可读且易于理解
第6行：使用-ne代替-lt。这将确保即使参数数量超过3（不仅少于3），您的脚本也会失败
您不需要在代码中使用read（阅读read的手册页），因为您没有从fd读取行。您需要将参数的值存储在Line：2-4
如果使用while循环，请确保条件在完成时失败，以便执行突破循环。这样做的方法是使用您未在代码中使用的递增或递减计数器
确保将目录的绝对路径作为第三个参数传递。这样，当您$HOME或head

tail

使用head显示n中的第一个head -n [numlines]行的正确方法，tail

重要提示：另请阅读下面的Charles Duffy评论，他指出了非常重要的事情，不容错过。

Answer 2

find [directory] -type f | while read f; do tail -n [num_lines] "$f"; done

类似地，

find [directory] -type f | while read f; do head -n [num_lines] "$f"; done

命令中意外标记“fi”附近的语法错误

2 个答案: