Why does `htop` display `$'\t'` as `?` in `sort` command?

Question

I was running a pipe command with one section being the following:

sort -t $'\t'  -T . -k1,1g

When I was monitoring htop I saw this instead:

What is the reason behind this? Does this mean my command is wrong or is there something wrong with htop?

Answer 1

There’s nothing wrong with your command, htop replaces control characters with question marks:

(((unsigned char)data_c[j]) >= 32 ? ((unsigned char)data_c[j]) : '?')

(characters with values less than 32 are control characters).

Answer 2

The htop process manager displays $'\t' as ? in the sort command because it interprets the \t as a tab character, which is not a valid sorting option.

In the sort command, \t is used as a delimiter to specify the field that the command should sort by. However, in htop, it is not a valid delimiter and is therefore displayed as ? in the sort column.

You can try to use the -k option to specify the sort field and the -t option to specify the delimiter. For example, htop -u -p -k 2,2 -t ' ' sorts by the 2nd field using a space as a delimiter.