If I use < to represent the setting "align left" and > to represent the setting "align right" what symbol should I use for "align center"? Is there any de facto standard for this? The symbol has to be an ASCII character the user can type on a US keyboard layout.

Context

I am working on the command line interface of a console application for Unix-like operating systems that can output pseudographical tables, like so:

┌─────┬─────┬────────┬─────┐
│ PID │ TTY │  TIME  │ CMD │
├─────┼─────┼────────┼─────┤
│ 8580│pts/1│00:00:00│  ps │
├─────┼─────┼────────┼─────┤
│28075│pts/1│00:00:01│ zsh │
└─────┴─────┴────────┴─────┘

The application can be told to align the text in each column left, right or center. To make it do that the user gives it the command line option -align LIST where LIST is a list of words "left", "right" or "center" where each word corresponds to one column, e.g., -align 'left left right center'.

I found that having to write each word in full takes too much effort. I intend to introduce l (a small L), r and c as shortcuts (which has precedent in LaTeX) but I also want to offer another, more graphical set of shortcut characters that would be easier to understand at a glace, say, when reading a shell script. Since using <, > for "left" and "right" respectively seems inevitable I am looking for the third unknown symbol to go with those two.