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Tcl provides a number of built-in functions (procedures) for various operations. Tcl includes below listed built-in functions −

• Functions for list handling.
• Functions for string handling.
• Functions for array handling.
• Functions for dictionary handling.
• Functions for File I/O handling.
• Functions for creating namespaces and packages in Tcl Built-in function.
• Functions for Math operations.
• Functions for System operations.

Each of the above except for math and system functions are covered in earlier chapters. Math and system built-in functions are explained below.

Math Functions

The math functions available in Tcl are listed in the following table −

Some examples using math functions are given below −

#!/usr/bin/tclsh

namespace import ::tcl::mathfunc::*
puts [tan 10]
puts [pow 10 2]
puts [ceil 10.34]
puts [hypot 10 20]
puts [srand 45]
puts [log 10]
puts [srand 45]

When the above code is executed, it produces the following result −

0.6483608274590866
100.0
11.0
22.360679774997898
0.0003521866166741525
2.302585092994046
0.0003521866166741525

System Functions

The important system functions in Tcl includes,

• clock − seconds function, which returns current time in seconds.
• clock − format function, which formats the seconds into date and time.
• clock − scan function, which scans the input string and converts it into seconds.
• open − function, which is used to open a file.
• exec − function, which is used to execute a system command.
• close − function, which is used to close a file.

Some examples for the above functions are listed below −

#!/usr/bin/tclsh

#get seconds
set currentTime [clock seconds]
puts $currentTime
#get format 
puts "The time is: [clock format $currentTime -format %H:%M:%S]"
puts "The date is: [clock format $currentTime -format %D]"

set date "Jun 15, 2014"
puts [clock scan $date -format {%b %d, %Y}]

puts [exec ls]
puts [exec dir]

set a  [open input.txt]
puts [read $a];
puts $a
close $a

When the above code is executed, it produces the following result −

1402819756
The time is: 03:09:16
The date is: 06/15/2014
1402808400
input.txt
main.tcl
input.txt  main.tcl
This is the file you can use to provide input to your program and later on open
   it inside your program to process the input.

file3

The following table provides the list strings that can be used to format the date and time.

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