tparmchar

The `tparmchar` function is a utility in Unix-like operating systems, commonly used to parse terminal parameter strings and extract specific values. It is part of the termcap and terminfo databases, which define characteristics of various terminal types. The function is particularly useful in applications that need to dynamically retrieve terminal capabilities, such as terminal emulators, shell scripts, or text-based user interfaces.

The primary purpose of `tparmchar` is to format a string containing terminal capabilities according to the specified parameters. Unlike `tparm`, which returns a string containing terminal capabilities, `tparmchar` appends the formatted string to a provided character buffer. This distinction allows for more flexible handling of terminal parameter strings, especially when working with fixed-size buffers or when concatenating multiple capabilities.

The function takes several arguments: a pointer to a character buffer where the result will be stored, the maximum length of the buffer, and a variable number of parameters. The parameters can include terminal capabilities (e.g., `cl`, `cr`, `up`) or special codes like `%p1%` to insert numeric values. For example, `tparmchar(buf, sizeof(buf), "up", 10)` would generate a string that moves the cursor up 10 lines, assuming "up" is a valid capability for the terminal.

`tparmchar` is often used in conjunction with functions like `tgetstr` or `tgetnum` to retrieve terminal capabilities from the termcap or terminfo database. It is particularly useful in legacy systems or applications that require precise control over terminal output formatting. While modern terminal handling libraries (such as ncurses) provide more robust alternatives, `tparmchar` remains relevant in environments where compatibility with older systems is necessary.