My approach is to put everything from the device onto the end of
a string variable, which I'll refer to by its name, "outb".
This variable is dynamic in that it is allowed to grow as
required, and gets trimmed (one way or another) as data is
removed.

When parsing outb, I look for result identifiers, like "+CBM: "
and "+CSQ: ", and store the positions of the first instances of
these into appropriate variables, like this in C:

   ccedpos = strstr(outb, "+CCED: ");
   cbmpos = strstr(outb, "+CBM: ");
   csqpos = strstr(outb, "+CSQ: ");

Then I'll usually find which of these positions is the earliest
(smaller address offset), and process that one first in a
routine specific to its data.  Then I'll destroy the identifier
within outb (by changing "+CSQ: " to "-CSQ: " for example).
Then I'll repeat the above piece of code, find the next result,
and process it.  When no identifier is to be found, I'll empty
outb:

   outb[0] = 0;

This approach implies lingering long enough on reading the input
buffer to wait for results to arrive fully and intact.

Part of the routine to handle "+CSQ: " results looks like this:

   csqpos[0] = '-';
   csqpos += 6;
   if (sscanf(csqpos, "%2d%*[,]", &rxlv) != 1) rxlv = 0;
   if (rxlv) rxlv = (2 * rxlv) - 113;  // convert to dBm
   if (rxlv > 0) rxlv = 0;

so I'm not concerned here about trailing <cr> or <lf> characters
at all.

I find the above works well for most mixes of immediate and
unsolicited-result commands.  Minor exceptions include the
software user requesting the device IMEI.  This is catered for
like this:

   Writecmd(1, 0, okresp, "ATE1\r");
   Writecmd(2, 0, "AT+CGSN", "AT+CGSN\r");
   Writecmd(1, 0, okresp, "ATE0\r");
   if (tmpp1 = strstr(outb, "AT+CGSN")) {
     tmpp1[3] = ' ';
     if (sscanf(tmpp1, "%*[^0-9]%15[0-9]%*[\r\nOK]", &tmpca1)
!= 1) tmpca1[0] = 0;
   }
   if (strlen(tmpca1) == 15) cprintf("\rIMEI: %s\r\n", tmpca1);
   else cprintf("\rCannot read the IMEI at present.\r");

Here, the four "Writecmd" routine's arguments are:

   seconds to wait for expected response

   clear outb first (0 = no, 1 = yes)

   the string to expect (okresp = "\r\nOK\r\n")

   the command to the device.

This is part of a comprehensive netmonitoring program for a
Wavecom modem, and there many other twists and turns to the
processing of course.

John