A  _c_o_m_p_r_e_s_s_i_o_n  program reduces the size of a file. Compres-
sion can be applied to files of all types, including  sound-
files, ASCI text files and executable binary files. Compres-
sion is frequently applied to files before they are archived
to  a  data  tape, removable disk (e.g. a Zip, Orb or floppy
disk) or a data cmpact disc, enabling  us  to  squeeze  more
files  onto the archive storage medium. However, compression
can also be usefully applied to any  large  file  that  will
remain  on  a  hard disk, but which will not be needed for a
while.  This reduces the amount of disk  space  consumed  by
the file.

Files that have been compressed are not immediately or fully
usable with many standard Unix or  music  software  commands
while  in  this  compressed  state.   Compressed  files  are
restored to their original, fully usable state  by  applying
an _u_n_c_o_m_p_r_e_s_s operation.

General purpose Unix/Linux compression programs such as _g_z_i_p
and _b_z_i_p_2, discussed in section 2 below, can be  applied  to
files  of  all  types.   However,  we do _n_o_t recommend using
these general purpose utilities as the  principal  means  of
reducing  the  size of _s_o_u_n_d_f_i_l_e_s, because they are not very
effective for this task.   Substantially  greater  soundfile
compression  can  be obtained by using programs specifically
designed for this purpose.

11..  SSoouunnddffiillee ccoommpprreessssiioonn

On the ECMC Linux and SGI systems,  we  currently  recommend
the program _s_h_o_r_t_e_n for soundfile compression and subsequent
uncompression. _s_h_o_r_t_e_n can be run either directly, with  the
_s_h_o_r_t_e_n  command, or else (somewhat more easily) by means of
the ECMC scripts  _r_u_n_s_f_c_o_m_p_r_e_s_s  and  _r_u_n_s_f_u_n_c_o_m_p_r_e_s_s.   The
_L_i_n_u_x and _S_G_I versions of _s_h_o_r_t_e_n (and thus also of _r_u_n_s_f_o_m_-
_p_r_e_s_s) differ in a few important respects.  For  information
on  using  _s_h_o_r_t_e_n and the _r_u_n_s_f_c_o_m_p_r_e_s_s and _r_u_n_s_f_u_n_c_o_m_p_r_e_s_s
scripts, consult the following sources:

     +o Section 6 of the _E_C_M_C _U_s_e_r_s_' _G_u_i_d_e
     +o The online or hardcopy Linux and SGI _m_a_n  pages   for
     _r_u_n_s_f_c_o_m_p_r_e_s_s and _s_h_o_r_t_e_n. (Note that the _m_a_n pages for
     _s_h_o_r_t_e_n differ on the SGI and Linux systems, reflecting
     differences  in  the SGI and Linux versions of the pro-
     gram itself.)

The _t_a_r program (or, more often,  the  ECMC  variant  _t_a_r_s_f)
often  is  used in conjunction with _s_h_o_r_t_e_n_/_r_u_n_s_f_c_o_m_p_r_e_s_s as
well as with _g_z_i_p or _b_z_i_p_2 to  achieve  maximum  compression
for  archiving  multiple  soundfiles  to tapes or disks. See
Section 6 of the _E_C_M_C _U_s_e_r_s_' _G_u_i_d_e or the _e_c_m_c_h_e_l_p file  _t_a_r
for  a  quick  overview  of using _t_a_r and _t_a_r_s_f, and the SGI
_m_a_n, Linux _m_a_n or Linux _i_n_f_o page on _t_a_r for  full  details.
The  GNU/Linux and SGI versions of _t_a_r are identical in many
respects, but the GNU version includes more options and time
saving features.

22..  CCoommppaaccttiinngg ffiilleess wwiitthh _g_z_i_p or _b_z_i_p_2

_g_z_i_p  currently is the most widely used general purpose com-
pression program on Linux/Unix systems.  One reason for this
popularity  is  cross-platform  support.   Certain  types of
gzipped files -- notably gzipped _t_a_r archive files  --  also
can  be  uncompressed  and extracted on Windows systems with
the _W_i_n_z_i_p utility (available on the ECMC Windows  systems).

_b_z_i_p_2  is a more recent general purpose Linunx/Unix compres-
sion program that often provides 20 % or more  greater  com-
pression  than  _g_z_i_p.   However, it is less frequently used,
and bzipped  files  currently  cannot  be  uncompressed  and
extracted  by  _W_i_n_z_i_p on Windows systems.  Unix-based Macin-
tosh systems (OS X and higher) include both _g_z_i_p and  _b_z_i_p_2.

The  commands  used  to   compress and uncompress files with
_g_z_i_p and _b_z_i_p_2 are very similar:

To _c_o_m_p_r_e_s_s one or more files:
     _g_z_i_p  _f_i_l_e_n_a_m_e  _[_f_i_l_e_n_a_m_e_2  _f_i_l_e_n_a_m_e_N_]
     or
     _b_z_i_p_2  _f_i_l_e_n_a_m_e  _[_f_i_l_e_n_a_m_e_2  _f_i_l_e_n_a_m_e_N_]
_g_z_i_p will append the extension _._g_z to  the  compressed  file
names.  _b_z_i_p_2  will  append  the file name extension _._b_z_2 to
files it compresses.

To view an ASCII file that has been compressed you can type
     _z_c_a_t  _f_i_l_e_n_a_m_e (for _g_z_i_p_p_e_d files) or
     _z_c_a_t  _f_i_l_e_n_a_m_e  (for files that  have  been  compressed
     with _b_z_i_p_2).

To  _u_n_c_o_m_p_r_e_s_s  (decompress)  files,  you can use any of the
variant commands below. _g_z_i_p allows you to omit the _._g_z file
name  extension  of  the compressed input files. With _b_z_i_p_2,
however, you must type in the complete input file names (you
cannot omit the _._b_z_2 extension.
     _g_z_i_p _-_d  _f_i_l_e_n_a_m_e  _[_f_i_l_e_n_a_m_e_2  _f_i_l_e_n_a_m_e_N_]
     or
     _g_z_i_p _-_-_d_e_c_o_m_p_r_e_s_s  _f_i_l_e_n_a_m_e  _[_f_i_l_e_n_a_m_e_2  _f_i_l_e_n_a_m_e_N_]
     or
     _g_u_n_z_i_p  _f_i_l_e_n_a_m_e  _[_f_i_l_e_n_a_m_e_2  _f_i_l_e_n_a_m_e_N_]

     _b_z_i_p_2 _-_d _f_i_l_e_n_a_m_e_._b_z_2  _[_f_i_l_e_n_a_m_e_2_._b_z_2  _f_i_l_e_n_a_m_e_N_._b_z_2_]
     or
     _b_z_i_p_2 _-_-_d_e_c_o_m_p_r_e_s_s  _f_i_l_e_n_a_m_e_._b_z_2  _[_f_i_l_e_n_a_m_e_2_._b_z_2  _f_i_l_e_-
     _n_a_m_e_N_._b_z_2_]
     _b_u_n_z_i_p_2  _f_i_l_e_n_a_m_e_._b_z_2  _[_f_i_l_e_n_a_m_e_2_._b_z_2  _f_i_l_e_n_a_m_e_N_._b_z_2_]

Wild card characters (chiefly *)  can  be  used  to  specify
groups of files:
     _g_z_i_p  _t_e_m_p_*
will  cause  _g_z_i_p to compress all files in your current Unix
directory that begn with the character string "temp."
     _b_z_i_p_2 _-_d  _$_S_F_D_I_R_/_*_._b_z_2
will cause _b_z_i_p_2 to decompress all  files  in  your  current
working  soundfile  directory that have been previously com-
pressed with _b_z_i_p_2.

To display a list of additional command options type:
     _g_z_i_p  _-_h   or _b_z_i_p_2  _-_h

                     Last updated 6/01

