bash - 什么是 | tr -d 在 bash 中做什么？

Question

有人可以解释一下这段代码在做什么吗？

if [ -f "saved.txt" ]; then                // What does -f do?
    rm saved.txt
fi

in=$(echo "{query}" | tr -d "\\")          // How does this work? 
                                           // What does | tr -d "\\" mean?

echo "$in" > saved.txt                     // Is this simply putting the 
                                           // value of $in into saved.txt?

Answer 1

最初的 if 语句将测试该文件是否是常规文件。更多关于file test operators here .

此脚本将回显字符 {query} 并将其传送到命令 tr，该命令使用 -d 将删除那些字符被指定。 tr 代表翻译。在这种情况下，它需要一个 SET，并且根据手册页，如果您使用 \\，它将删除反斜杠。

结果存储在$in中。

最后将存储在in中的结果输出到saved.text中。

NAME tr - translate or delete characters

SYNOPSIS tr [OPTION]... SET1 [SET2]

DESCRIPTION Translate, squeeze, and/or delete characters from standard input, writing to standard output.

   -c, -C, --complement
          first complement SET1

   -d, --delete
          delete characters in SET1, do not translate

   -s, --squeeze-repeats
          replace  each  input  sequence  of  a repeated character that is listed in SET1 with a single occurrence of that
          character

   -t, --truncate-set1
          first truncate SET1 to length of SET2

   --help display this help and exit

   --version
          output version information and exit

   SETs are specified as strings of characters.  Most represent themselves.  Interpreted sequences are:

   \NNN   character with octal value NNN (1 to 3 octal digits)

   \\     backslash