Android won't let me change configuration file
/proc does not contain actual files, and it's not part of the /system directory. It is, as described by the Linux manual:


  The proc filesystem is a pseudo-filesystem which provides an interface to kernel data structures.  It is commonly mounted at /proc.  Most of it is read-only, but some files allow kernel variables to be changed.


In other words, it is a "virtual" filesystem that allows for file like access to certain kernel data. You cannot modify these handles by editing them the way you are hoping to.

If the data you need to change allows for modifications through /proc, it generally needs to be done using something like cat or echo to write a new value to the handle. However, according to the ALSA documentation, both /proc/asound/cards and /proc/asound/pcm are read-only structures.

You'll need to find another way to accomplish your goal, perhaps by changing some underlying configuration file that controls ALSLA on your device. On traditional Linux desktops, it's typically/etc/asound.conf, but your device's ROM may not expose these configuration settings in the same manner, or it may be hard-coded to populate the /proc entries without actually using a config file. Based on what I've seen, if your device does support the config file, it's generally in /system/etc/asound.conf.