“ls:未找到"运行“读取路径"后 [英] "ls: not found" after running "read PATH"

问题描述

我正在尝试编写一个小脚本来列出给定变量中的目录.但是，在将输入读入变量 PATH 后，我根本无法运行 ls.

I'm trying to write a little script to list a directory from a given variable. However, I can't run ls at all after reading my input into the variable PATH.

#!/system/bin/sh 
echo "enter directory for listing"
read "PATH"

ls "$PATH" -R > list.txt

退出:

ls: not found

...并且不向 list.txt 写入任何内容.

...and writes nothing to list.txt.

推荐答案

变量名 PATH 已被保留用于不同的目的:它列出了所有可能的位置搜索以查找未内置到壳.

The variable name PATH is already reserved for a different purpose: It lists all the possible locations searched to find commands not built into the shell.

ls 就是这样一个命令.因此，当您更改 PATH 的值时，您会更改 shell 尝试查找 ls 可执行文件的方式；除非 PATH 的新值包含一个带有 ls 可执行文件的目录，否则任何进一步尝试运行 ls(或其他未内置的命令)外壳)将失败.

ls is such a command. Thus, when you change the value of PATH, you change the way the shell tries to look for the ls executable; unless the new value of PATH includes a directory with a ls executable in it, any further attempts to run ls (or other commands not built into the shell) will fail.

相反，使用不同的变量名称 - 理想情况下，至少包含一个小写字符，以避免与(全大写)内置变量和环境变量发生冲突.

Instead, use a different variable name -- ideally, including at least one lower-case character, to avoid conflict with (all-uppercase) builtins and environment variables.

因此，一种更正的形式可能是:

Thus, one corrected form might be:

#!/system/bin/sh 
echo "enter directory for listing"
IFS= read -r path

ls -R -- "$path" > list.txt

请注意，在这种情况下，-R 被移动到 "$path" 之前——而 GNU 系统允许可选参数在位置参数之后，许多较旧的UNIX 系统只会将标志(如 -R)视为有效，如果它们在第一个非标志/选项参数之前被找到.

Note that the -R is moved before the "$path" in this case -- while GNU systems will allow optional arguments to be after positional arguments, many older UNIX systems will only treat flags (like -R) as valid if they're found before the first non-flag/option argument.

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