linux - 执行已知已安装的可执行文件时遇到问题

Question

我最近在我的 Arch 系统上安装了 PyQt4 和 PyQt5，但是当我在终端中运行“qmlviewer”时，它返回:

qmlviewer: could not exec '/usr/lib/qt/bin/qmlviewer': No such file.

我知道我有 qmlviewer - locate 返回我有 qmlviewer 的几个目录。它只是不在我的终端正在执行的目录中。如何让我的终端尝试从实际所在的目录执行 qmlviewer？

Answer 1

bash 跟踪命令所在的位置。 (否则它必须每次都搜索 PATH。)当可执行文件被移动时(如升级过程中可能发生的情况)，shell 将不知道其路径信息已过时。解决方案是运行 hash -r 来清除 shell 内存中的路径位置。下次您尝试运行可执行文件时，bash 将从头开始搜索 PATH 来查找它。

我们将进行一些实际的演示。让我们创建一个名为 cmd1 的新命令:

# cp /bin/date /bin/cmd1
# cmd1
Tue Mar 18 22:27:23 PDT 2014

bash 必须搜索 PATH 才能找到 cmd1，但是一旦完成，它就会记住，如 type 命令所示:

# type cmd1
cmd1 is hashed (/bin/cmd1)

现在，让我们通过移动命令来欺骗 bash:

# mv /bin/cmd1 /usr/bin/cmd1
# cmd1
bash: /bin/cmd1: No such file or directory

解决方案如下:

# hash -r
# cmd1
Tue Mar 18 22:28:20 PDT 2014
# type cmd1
cmd1 is hashed (/usr/bin/cmd1)

man bash的相关部分是:

 hash -rv command ...
        The shell maintains a hash table which remembers the loca‐
        tions of commands.  With no arguments whatsoever, the hash
        command prints out the contents of this table.  Entries
        which have not been looked at since the last cd command
        are marked with an asterisk; it is possible for these
        entries to be invalid.

        With arguments, the hash command removes the specified
        commands from the hash table (unless they are functions)
        and then locates them.  With the -v option, hash prints
        the locations of the commands as it finds them.  The -r
        option causes the hash command to delete all the entries
        in the hash table except for functions.

POSIX 中包含了 hash 函数的功能稍少的版本。 .