为什么我的PATH被忽略? [英] Why is my PATH ignored?

问题描述

尽管我的Unix PATH包括/Library/TeX/texbin，但我的PATH的这一部分似乎被忽略了.例如，当我尝试

pdftex --version

我知道

-bash:pdftex:找不到命令

同时

/Library/TeX/texbin/pdftex --version

按预期工作.

类似地，

其中-a pdftex

没有结果.

我的PATH来自两个来源:/private/etc/paths，其中包含

/Users/Rax/.cabal/bin
/usr/local/bin
/usr/bin
/bin
/usr/sbin
/sbin
/Users/Rax/bin

以及/private/etc/paths.d/40-XQuartz和/private/etc/paths.d/TeX中的两个其他文件，分别包含

/opt/X11/bin

和

/Library/TeX/texbin

这3个文件一起产生预期的PATH

$ echo $PATH
/Users/Rax/.cabal/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/Rax/bin:/opt/X11/bin:/Library/TeX/texbin

可以按预期找到其他目录中的所有条目(包括/opt/X11/bin中的条目)，但是最后一个条目似乎被忽略了(至少在查找可执行文件时).

为什么我的PATH的一部分会被忽略?我该如何确保它不存在，以便在那里按预期找到可执行文件?

---

OS X 10.11.3

解决方案

在注释中已对此进行了整理，但我将作为记录的答案进行发布:问题是由于PATH中的不可见字符引起的，这被解释为实际目录名称的一部分.具体来说，它的末尾是一个空格，但是您可以从许多其他不可见字符中获得相同的效果. (我实际上是在猜测path.d中的文件之一是DOS/Windows文本格式，并且在行尾有回车符.)

要使不可见字符更加可见，可以使用printf或cat -vet:

$ printf "%q\n" "$PATH"
/Users/Rax/.cabal/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/Rax/bin:/opt/X11/bin:/Library/TeX/texbin\ 
$ echo "$PATH" | LC_ALL=c cat -vet
/Users/Rax/.cabal/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/Rax/bin:/opt/X11/bin:/Library/TeX/texbin $

请注意在printf输出末尾的\-它后面实际上是一个空格，但是您必须推断-在cat -vet输出中$之前的空格.顺便说一句，将$PATH的引用放在双引号中非常重要，因为没有它们，空格将被剪裁.

如果原来是回车，则显示为:

$ printf "%q\n" "$PATH"
$'/Users/Rax/.cabal/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/Rax/bin:/opt/X11/bin:/Library/TeX/texbin\r'
$ echo "$PATH" | LC_ALL=c cat -vet
/Users/Rax/.cabal/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/Rax/bin:/opt/X11/bin:/Library/TeX/texbin^M$

在这种情况下，printf将回车符显示为\r(并将整个内容包装在$' ... '中以指示应解释转义符)，而cat -vet将其显示为^M.

Although my Unix PATH includes /Library/TeX/texbin this component of my PATH appears to be ignored. For example, when I try

pdftex --version

I get

-bash: pdftex: command not found

while

/Library/TeX/texbin/pdftex --version

works as expected.

Similarly,

where -a pdftex

gives no results.

My PATH is built from two sources: /private/etc/paths, which contains

/Users/Rax/.cabal/bin
/usr/local/bin
/usr/bin
/bin
/usr/sbin
/sbin
/Users/Rax/bin

and two additional files in /private/etc/paths.d/40-XQuartz, and /private/etc/paths.d/TeX, which contain, respectively

/opt/X11/bin

and

/Library/TeX/texbin

Together these 3 files result in the expected PATH

$ echo $PATH
/Users/Rax/.cabal/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/Rax/bin:/opt/X11/bin:/Library/TeX/texbin

All the entries in the other directories are found as expected (inclusion those in /opt/X11/bin) but the last entry appears to be ignored (at least when locating executables).

Why is part of my PATH being ignored? How do I ensure that it is not, so that executables there are found as expected?

---

OS X 10.11.3

解决方案

This got sorted out in the comments, but I'll post as an answer for the record: the problem was due to an invisible character in the PATH, that was being interpreted as part of the actual directory name. Specifically, it was a space at the end, but you could get the same effect from a number of other invisible characters. (I was actually guessing that one of the files in paths.d was in DOS/Windows text format, and had a carriage return at the end of the line.)

To make invisible characters more visible, you can use printf or cat -vet:

$ printf "%q\n" "$PATH"
/Users/Rax/.cabal/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/Rax/bin:/opt/X11/bin:/Library/TeX/texbin\ 
$ echo "$PATH" | LC_ALL=c cat -vet
/Users/Rax/.cabal/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/Rax/bin:/opt/X11/bin:/Library/TeX/texbin $

Note the \ at the end of the printf output -- it's actually followed by a space, but you have to infer that -- and the space before the $ in the cat -vet output. BTW, it's very important to put the reference to $PATH in double-quotes, since without them the space would've been trimmed.

If it had been a carriage return instead, here's what it would have looked like:

$ printf "%q\n" "$PATH"
$'/Users/Rax/.cabal/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/Rax/bin:/opt/X11/bin:/Library/TeX/texbin\r'
$ echo "$PATH" | LC_ALL=c cat -vet
/Users/Rax/.cabal/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/Rax/bin:/opt/X11/bin:/Library/TeX/texbin^M$

In this case, printf shows the carriage return as \r (and wraps the whole thing in $' ... ' to indicate that escapes should be interpreted), while cat -vet shows it as ^M.

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