HP-UX Reference (11i v1 05/09) - 1 User Commands N-Z (vol 2)

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sh-posix(1) sh-posix(1)

Some very old shell scripts use a caret (

ˆ) as a synonym for the pipe character (|). sh does not recognize

the caret as a pipe character.

If a command is piped into a shell command, all variables set in the shell command are lost when the com-

mand completes.

Using the

fc built-in command within a compound command will cause the entire command to disappear

from the history ﬁle.

The dot (.) special command, as in

. ﬁle, reads the entire ﬁle before any commands are executed. There-

fore,

alias and unalias commands in the ﬁle will 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

SIGCHLD is not

executed until the foreground job terminates.

The

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

exported to the environment.

Background processes started from a noninteractive shell cannot be accessed with job control commands.

The value of the IFS variable in the user’s environment affects the behavior of scripts.

Collating Order

In an international environment, character ordering is determined by the value 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 (see regexp(5)) 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 noninternationalized 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, and so on, be set to C or not set at all.

The history ﬁle does not support mixing of locales in the same ﬁle. For users of multiple locales, you can

assign a unique history ﬁle for each locale by setting HISTFILE as:

HISTFILE=$HOME/.sh_hist_${LANG}

The contents of here-documents

are stored in temporary ﬁles named

/var/tmp/sh<pid>.<number>.

Care is taken to remove these temporary ﬁles after their usage.

However, due to design limitations, in some cases these temporary ﬁles may still continue to exist after the

shell exits.

AUTHOR

sh was developed by AT&T, OSF, and HP.

FILES

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

/etc/passwd To ﬁnd home directories

/etc/profile Read to set up system environment

/etc/suid_profile Security proﬁle

/var/tmp/sh* For here-documents if /var/tmp is accessible

/tmp/sh* For here-documents if /var/tmp is not accessible

/usr/bin/sh Shell executable program location