HP-UX Reference (11i v2 07/12) - 1 User Commands A-M (vol 1)

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ksh(1) ksh(1)

The built-in command . ﬁle reads the entire ﬁle before any commands are executed. Therefore,

alias

and unalias commands in the ﬁle do not apply to any functions deﬁned in the ﬁle.

Traps are not processed while the shell is waiting for a foreground job. Thus, a trap on

CHLD is not exe-

cuted until the foreground job terminates.

The

export built-in command does not handle arrays properly. Only the ﬁrst element of an array is

exported to the environment.

Background processes started from a non-interactive shell cannot be accessed by using job control com-

mands.

In an international environment, character ordering is determined by the setting of

LC_COLLATE ,rather

than by the binary ordering of character values in the machine collating sequence. This brings with it cer-

tain attendant dangers, particularly when using range expressions in ﬁle name generation patterns. For

example, the command,

rm [a-z]*

might be expected to match all ﬁle names beginning with a lowercase alphabetic character. However, if

dictionary ordering is speciﬁed by

LC_COLLATE , it would also match ﬁle names beginning with an upper-

case character (as well as those beginning with accented letters). Conversely, it would fail to match letters

collated after z in languages such as Danish or Norwegian.

The correct (and safe) way to match speciﬁc character classes in an international environment is to use a

pattern of the form:

rm [[:lower:]]*

This uses LC_CTYPE to determine character classes and works predictably for all supported languages and

codesets. For shell scripts produced on non-internationalized systems (or without consideration for the

above dangers), it is recommended that they be executed in a non-NLS environment. This requires that

LANG, LC_COLLATE, etc., be set to "C" or not set at all.

Be aware that the value of the IFS variable in the user’s environment affects the behavior of scripts.

ksh implements command substitution by creating a pipe between itself and the command. If the root ﬁle

system is full, the substituted command cannot write to the pipe. As a result, the shell receives no input

from the command, and the result of the substitution is null. In particular, using command substitution for

variable assignment under such circumstances results in the variable being silently assigned a NULL value.

The contents of here-documents

are stored in temporary ﬁles named /tmp/shpid.number. Care is

taken to remove these temporary ﬁles after their usage. However, because of design limitations, some of

these temporary ﬁles may not be removed.

AUTHOR

ksh was developed by AT&T.

FILES

/etc/passwd to ﬁnd home directories

/etc/profile read to set up system environment

/etc/suid_profile security proﬁle

$HOME/.profile read to set up user’s custom environment

/tmp/sh* for here-documents