Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
lindex(n)		     Tcl Built-In Commands		     lindex(n)

______________________________________________________________________________

NAME
       lindex -	Retrieve an element from a list

SYNOPSIS
       lindex list ?index ...?
______________________________________________________________________________

DESCRIPTION
       The  lindex command accepts a parameter,	list, which it treats as a Tcl
       list. It	also accepts zero or more indices into the list.  The  indices
       may  be	presented either consecutively on the command line, or grouped
       in a Tcl	list and presented as a	single argument.

       If no indices are presented, the	command	takes the form:

	      lindex list

       or

	      lindex list {}

       In this case, the return	value of lindex	is simply  the	value  of  the
       list parameter.

       When presented with a single index, the lindex command treats list as a
       Tcl list	and returns the	index'th element from  it  (0  refers  to  the
       first element of	the list).  In extracting the element, lindex observes
       the same	rules concerning braces	and quotes and backslashes as the  Tcl
       command interpreter; however, variable substitution and command substi-
       tution do not occur.  If	index is negative or greater than or equal  to
       the number of elements in value,	then an	empty string is	returned.  The
       interpretation of each simple index value is the	same as	for  the  com-
       mand string index, supporting simple index arithmetic and indices rela-
       tive to the end of the list.

       If additional index arguments are supplied, then	each argument is  used
       in  turn	to select an element from the previous indexing	operation, al-
       lowing the script to select elements from sublists.  The	command,

	      lindex $a	1 2 3

       or

	      lindex $a	{1 2 3}

       is synonymous with

	      lindex [lindex [lindex $a	1] 2] 3

EXAMPLES
       Lists can be indexed into from either end:

	      lindex {a	b c} 0
		    -_ a
	      lindex {a	b c} 2
		    -_ c
	      lindex {a	b c} end
		    -_ c
	      lindex {a	b c} end-1
		    -_ b

       Lists or	sequences of indices allow selection into lists	of lists:

	      lindex {a	b c}
		    -_ a b c
	      lindex {a	b c} {}
		    -_ a b c
	      lindex {{a b c} {d e f} {g h i}} 2 1
		    -_ h
	      lindex {{a b c} {d e f} {g h i}} {2 1}
		    -_ h
	      lindex {{{a b} {c	d}} {{e	f} {g h}}} 1 1 0
		    -_ g
	      lindex {{{a b} {c	d}} {{e	f} {g h}}} {1 1	0}
		    -_ g

       List indices may	also perform limited computation, adding or  subtract-
       ing fixed amounts from other indices:

	      set idx 1
	      lindex {a	b c d e	f} $idx+2
		    -_ d
	      set idx 3
	      lindex {a	b c d e	f} $idx+2
		    -_ f

SEE ALSO
       list(n),	  lappend(n),  linsert(n),  llength(n),	 lsearch(n),  lset(n),
       lsort(n), lrange(n), lreplace(n), string(n)

KEYWORDS
       element,	index, list

Tcl				      8.4			     lindex(n)

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | KEYWORDS

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=lindex.tcl86&manpath=FreeBSD+13.0-RELEASE+and+Ports>

home | help