z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

If the shell command is operating on a character string and not on a byte string,
and the shell is in a locale that supports DBCS, and if the utility encounters an
invalid DBCS string, such as the ones described in this topic—you get an “illegal
byte sequence” message and the utility may fail.
Note: newline (\n [0x15]) causes the shift state of any subsequent character
sequence to start in the initial state (shifted into the SBCS mode). This may
apply when a command is processing a DBCS string and encounters
newline before a “shift in.”
For information on rules for creating DBCS data, refer to DBCS Design
Guide—System/370 Software , GG18-9095.
Displaying DBCS characters
In a doublebyte environment, column positions are always based on the width of
narrow characters. Normally, characters are “thin”; they take up only one column
position when displayed. In contrast, some DBCS characters are “thick”; they take
up two column positions when displayed.
The number of actual characters that are displayed by the command in the column
area depends on the thickness of the characters. This applies to such commands
as ls, fold, and pr, which display DBCS characters in column positions.
Switching locales
By default, the shell starts in the POSIX locale and cannot handle DBCS text until
the locale is changed, typically with the shell command export LC_ALL=Ja_JP. This
export command affects the current shell environment with the following exception:
if you change the locale to DBCS, the shell’s LC_CTYPE locale category remains in
the locale until is replaced via the exec command (exec /bin/sh).
Even if you change the locale to DBCS by using export LC_ALL=Ja_JP, the shell’s
LC_CTYPE variable remains in the previous locale (initially POSIX) until the shell is
exec’d again with exec sh.
Always follow the export LC_ALL=your locale with exec sh to be sure the shell and
utilities are running in the desired locale. This is true even if you place the export
LC_ALL=your_locale in your login profile.
Problems with filenames containing DBCS characters
The file system treats all filenames as if they contained SBCS characters. However,
when you use the shell in the DBCS locale, filename and pathname comparison is
performed in wide mode. That is, all the characters in the name are converted to
wide characters before comparison. By doing this, the shift codes are removed from
the comparison and, therefore, a match can be found with the filenames.
For example, if you have such DBCS filenames as:
db/so dbfile1 si
db/so dbfile2 si
where so and si are the shift codes that shift out to DBCS and back to SBCS, then
when in the DBCS locale (Ja_JP),
ls db/so file si *
lists both files.
Chapter 1. Introduction to shell commands and DBCS 9