bash中的制表符竞争挂起“选择”

Question

Recently my tab completion in bash has become annoyingly slow. I enter part of a directory name and hit Tab , but it takes over a half second for the directory name to be completed. To debug, I ran strace on the shell process from another terminal while I ran the tab completion, and found that a call to "select" was taking up the time:

06:06:35.379778 select(1, [0], NULL, [0], {0, 500000}) = 0 (Timeout) 06:06:35.881344 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0

You can clearly see that the call to select times out after 500ms. I ran the same experiment in my local machine (this problem is happening on my company-provided VM) and observed that there is no call to select at all. My VM is running bash version 4.3.11(1)-release (x86_64-pc-linux-gnu) and my local machine is running 4.3.48(1)-release (x86_64-pc-linux-gnu)

How can I debug this further? Should I just upgrade bash?

---

In response to Emily's comment:

~: complete
~: complete -r
~: echo $PROMPT_COMMAND

~: trap
trap -- '' SIGTSTP
trap -- '' SIGTTIN
trap -- '' SIGTTOU

Answer 1

I had a similar problem. Plenty of disk space, plenty of CPU and memory, but tab completion would regularly hang for 0.5 to 1.5 seconds. I ran strace and also saw the hang was at a pselect.

I fixed it by changing the _tilde() function in /usr/share/bash-completion/bash-completion to always immediately return 0. It seems a comparison ( if [[ $1 == \\~* && $1 != */* ]]; then ... ) is taking a long time to complete.

Adding a " return 0 " at the beginning of the function made things go faster, and didn't seem to have any adverse effects.