1lindex(n)                    Tcl Built-In Commands                   lindex(n)
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NAME

8       lindex - Retrieve an element from a list
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SYNOPSIS

11       lindex list ?index ...?
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DESCRIPTION

15       The  lindex command accepts a parameter, list, which it treats as a Tcl
16       list. It also accepts zero or more indices into the list.  The  indices
17       may  be  presented either consecutively on the command line, or grouped
18       in a Tcl list and presented as a single argument.
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20       If no indices are presented, the command takes the form:
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22              lindex list
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24       or
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26              lindex list {}
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28       In this case, the return value of lindex is simply  the  value  of  the
29       list parameter.
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31       When presented with a single index, the lindex command treats list as a
32       Tcl list and returns the index'th element from  it  (0  refers  to  the
33       first element of the list).  In extracting the element, lindex observes
34       the same rules concerning braces and quotes and backslashes as the  Tcl
35       command interpreter; however, variable substitution and command substi‐
36       tution do not occur.  If index is negative or greater than or equal  to
37       the number of elements in value, then an empty string is returned.  The
38       interpretation of each simple index value is the same as for  the  com‐
39       mand string index, supporting simple index arithmetic and indices rela‐
40       tive to the end of the list.
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42       If additional index arguments are supplied, then each argument is  used
43       in  turn to select an element from the previous indexing operation, al‐
44       lowing the script to select elements from sublists.  The command,
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46              lindex $a 1 2 3
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48       or
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50              lindex $a {1 2 3}
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52       is synonymous with
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54              lindex [lindex [lindex $a 1] 2] 3
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EXAMPLES

57       Lists can be indexed into from either end:
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59              lindex {a b c} 0
60                    → a
61              lindex {a b c} 2
62                    → c
63              lindex {a b c} end
64                    → c
65              lindex {a b c} end-1
66                    → b
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68       Lists or sequences of indices allow selection into lists of lists:
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70              lindex {a b c}
71                    → a b c
72              lindex {a b c} {}
73                    → a b c
74              lindex {{a b c} {d e f} {g h i}} 2 1
75                    → h
76              lindex {{a b c} {d e f} {g h i}} {2 1}
77                    → h
78              lindex {{{a b} {c d}} {{e f} {g h}}} 1 1 0
79                    → g
80              lindex {{{a b} {c d}} {{e f} {g h}}} {1 1 0}
81                    → g
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83       List indices may also perform limited computation, adding or  subtract‐
84       ing fixed amounts from other indices:
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86              set idx 1
87              lindex {a b c d e f} $idx+2
88                    → d
89              set idx 3
90              lindex {a b c d e f} $idx+2
91                    → f
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SEE ALSO

94       list(n),   lappend(n),  linsert(n),  llength(n),  lsearch(n),  lset(n),
95       lsort(n), lrange(n), lreplace(n), string(n)
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KEYWORDS

98       element, index, list
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102Tcl                                   8.4                            lindex(n)
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