As mentioned in the Section called Executing Commands in the Chapter called Interacting with the GNO Shell, arguments are passed to a command to extend its usefulness. The arguments presented in the last chapter were words, such as foo, bar and foo.c. Standards exist under UNIX for programs to accept command-line option arguments. Option arguments (as the name suggests) are optional. There are two standards, short options and long options. Short options are characters that represent commands, whereas long options contain the entire option name.
Consider the following output of the CATALOG command from ProDOS:
/DEV NAME TYPE BLOCKS MODIFIED CREATED ENDFILE FINDER.DATA $C9 1 21-OCT-91 22:38 14-APR-90 18:24 260 FINDER.ROOT $C9 1 22-OCT-91 17:12 6-OCT-91 15:40 82 GENESYS DIR 1 21-OCT-91 23:37 25-APR-91 15:46 512 GSBUG DIR 1 21-OCT-91 23:38 19-JUL-90 16:48 512 MERLIN DIR 2 22-OCT-91 2:50 30-APR-91 20:21 1024 LIFEGUARD $B3 73 4-SEP-87 4:51 25-DEC-89 20:22 36608 ORCA DIR 2 22-OCT-91 17:12 14-SEP-89 18:27 1024 GNO DIR 2 22-OCT-91 17:12 13-AUG-91 16:36 1024 FAST.ANIM DIR 2 21-OCT-91 23:44 11-MAY-91 10:50 1024 MICOL DIR 2 22-OCT-91 3:10 14-JAN-90 2:46 1024 SRC DIR 1 21-OCT-91 23:44 7-AUG-91 20:30 512 NIFTYLIST DIR 2 21-OCT-91 23:44 29-JUL-91 4:04 1024 MCSRC DIR 1 21-OCT-91 23:45 7-AUG-91 20:34 512 BLOCKS FREE:43923 BLOCKS USED:21185 TOTAL BLOCKS:65108
It is impossible to get any variation in the format of this output. While the GNO/ME utility ls serves the same purpose as the command CATALOG from Applesoft BASIC, it has a wide number of options which can tailor the output to specific needs. Here is how ls can be used to give similar output to the CATALOG command:
gno% ls -l :dev total 45k drw--rd 0000 dir 512 Oct 21 23:45 1991 MCSrc drw--rd 0000 dir 1024 Oct 21 23:44 1991 NiftyList drw--rd 0000 dir 1024 Oct 21 23:44 1991 fast.anim drw--rd 0000 dir 512 Oct 21 23:37 1991 genesys drw--rd 0000 dir 1024 Oct 22 17:29 1991 gno drw--rd 0000 dir 512 Oct 21 23:38 1991 gsbug drw--rd 0000 dir 1024 Oct 22 02:50 1991 merlin drw--rd 0000 dir 1024 Oct 22 03:10 1991 micol drw--rd 0100 dir 1024 Oct 22 17:28 1991 orca drw--rd 0000 dir 512 Oct 21 23:44 1991 src
The -l short option argument tells ls to format the output in long format. ls supports only short options. If ls did support long options, the above command could be changed to ls +format-long. This is clearly more descriptive of what function ls will perform. For users to new to the UNIX environment, long format options are more user-friendly. However, advanced UNIX users prefer short options because of their brevity.
As indicated above, ls has a wide number of options available to format the output. Use the command "ls -?" to get a short list of these options. It is left as an exercise for the user to discover how these options affect the output of ls. For a complete description of the ls command and its options use the command man ls.
As an example of the usage and importance of long options, the following is the result of the +help option given to the coff utility. Note the use of both short and long options:
coff [-OPTIONS] filename [segment..] [loadsegment..] OPTIONS DESCRIPTION -v [+version] display coff's version number -D [+default] disable default options -d [+asm] dump segment body in 65816-format disassembly -T [+tool] interpret Toolbox, GS/OS, ProDOS, ROM calls -x [+hex] dump segment body in hex (can be used with '+asm') -l [+label] print expressions using labels (default is offsets) -t [+infix] display expressions in infix form -p [+postfix] display expressions in postfix form (default) -m [+merlin] format of '+asm' to use merlin opcodes (default) -o [+orca] format of '+asm' to use orca/m opcodes -a [+shorta] assume 8-bit accumulator for disassembly -i [+shorti] assume 8-bit index registers for disassembly -s [+header] dump segment headers only -n [+noheader] do not print segment headers -f [+nooffset] do not print offset into file -h [+help] print this information, then quit filename name of file to dump [segment] names of segments in file to dump [loadsegment] names of load segments in file to dump
The long options are much more descriptive, and provide a very easy way to remember options of programs. If an option passed to a shell utility program is not understood by that program, you will generally receive an error message stating that the option is not understood. If the program is user-friendly, a brief list of supported options will also be displayed.