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Full Discussion: error "test: [-d: unary operator expected" very confused.
Top Forums Shell Programming and Scripting error "test: [-d: unary operator expected" very confused. Post 302325282 by ahmad.diab on Sunday 14th of June 2009 10:05:09 AM
Old 06-14-2009
Equivalence of test, /usr/bin/test, [ ], and /usr/bin/[

these are commands and you can only use one of them:-

examples:-

if test -z "$1"
then
echo "No command-line arguments."
else
echo "First command-line argument is $1."
fi
echo
if /usr/bin/test -z "$1" # Equivalent to "test" builtin.
# ^^^^^^^^^^^^^ # Specifying full pathname.
then
echo "No command-line arguments."
else
echo "First command-line argument is $1."
fi
echo
if [ -z "$1" ] # Functionally identical to above code blocks.
# if [ -z "$1" should work, but...
#+ Bash responds to a missing close-bracket with an error message.
then
echo "No command-line arguments."
else
echo "First command-line argument is $1."
fi

if /usr/bin/[ -z "$1" ] # Again, functionally identical to above.
# if /usr/bin/[ -z "$1" # Works, but gives an error message.
# # Note:
# This has been fixed in Bash, version 3.x.
then
echo "No command-line arguments."
else
echo "First command-line argument is $1."
fi

Finally:-

The [[ ]] construct is the more versatile Bash version of [ ]. This is the extended test command, adopted from
ksh88.
No filename expansion or word splitting takes place between [[ and ]], but there is parameter expansion
and command substitution.
file=/etc/passwd
if [[ -e $file ]]
then
echo "Password file exists."
fi
Using the [[ ... ]] test construct, rather than [ ... ] can prevent many logic errors in scripts. For example,
the &&, ||, <, and > operators work within a [[ ]] test, despite giving an error within a [ ] construct.

 

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LEARN ABOUT OPENSOLARIS

echo

echo(3XCURSES)						  X/Open Curses Library Functions					    echo(3XCURSES)

NAME

       echo, noecho - enable/disable terminal echo

SYNOPSIS

       cc [ flag... ] file... -I /usr/xpg4/include  -L	/usr/xpg4/lib 
	-R  /usr/xpg4/lib  -lcurses  [ library... ]

       c89 [ flag... ] file... -lcurses [ library... ]

       #include <curses.h>

       int echo(void);

       int noecho(void);

DESCRIPTION

       The  echo()  function enables Echo mode for the current screen. The noecho() function disables Echo mode for the current screen. Initially,
       curses software echo mode is enabled and hardware echo mode of the tty driver is disabled. The echo() and noecho() functions control  soft-
       ware echo only. Hardware echo must remain disabled for the duration of the application, else the behavior is undefined.

RETURN VALUES

       Upon successful completion, these functions return OK. Otherwise, they return ERR.

ERRORS

       No errors are defined.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Unsafe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       getch(3XCURSES), getstr(3XCURSES), initscr(3XCURSES), libcurses(3XCURSES), scanw(3XCURSES), attributes(5), standards(5)

SunOS 5.11							    5 Jun 2002							    echo(3XCURSES)
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