linux - /system/bin/sh: cat:duty_pcts:I/O 错误

Question

linux命令cat有一些问题

#cd /sys/class/leds/green
# ls -al
....
-rw-rw-r-- root    root   4096  1970-01-02 08:00 duty_pcts
....
#cat duty_pctys

此时发生错误

__/system/bin/sh: cat:duty_pcts:I/O error__

Answer 1

该cat命令告诉您“嘿，我尝试读取名为 duty_pcts 的文件，但由于某种原因读取失败。我向操作系统询问errno变量中的错误代码，操作系统告诉我这是一个 I/O 错误（ EIO)。”

阅读 errno、open(2)、read(2) 和 close(2) 的手册页 [例如使用man 2 read] 并查看是否有任何系统调用可以设置errno为EIO。例如read(2)，您会发现，

   EIO    I/O error. This will happen for example when the process is in
          a background process group, tries to read from its controlling
          tty, and either it is ignoring or blocking SIGTTIN or its pro-
          cess group is orphaned.  It may also occur  when  there  is  a
          low-level I/O error while reading from a disk or tape.