04 Tcl字符串

append varName？value?

set var1 Hello 
set var2 World

append var1 $var2
=>HelloWorld

puts $var1
=>HelloWorld   # var1的内容被更改

# 使用格式
format spec value1 value2.....

set res [format "%2\$s" 1 5 9]

set str [format "%3\$s %1\$s %2\$s" "are" "right" "You"]
=> You are right

format "%x" 20
=>14                  # x表示无符号十六进制数

format "%8x" 20
=>      14            # 将20转变为8位十六进制数，右对齐

format "%08x" 20      # 将20转换为十六进制数，8位数据宽度，用0填补
=>00000014

format "%#08x" 20    # 将20进制转变为十六进制数，8位数据宽度，用0填补，添加前导Ox
=>0x000014

set c [format %c%e%c 40 30000 41]
=>(3.000000e+004)         # C表示将整数映射为ASCII字符，40和41对应“(”,“)”

set num [scan Aa %C Var1]
=>1                            # 将字符串Aa的第一个字符A转换为对应整数
                               # 并赋值给Var1变量，返回成功转换的个数
puts $Var1
=>65                           # 字符A对应的整数

scan string format var1?var?var?var?......

set num [scan "abcABC" "%C%C" var1 var2]
=>2

puts "$var1 $var2"
=>97 98

set num [scan "abcABC" "%C%C"]
=>97 98

puts $num
=>97 98                       # 没有制定输出变量的结果

# 格式描述说明要扫描小写a-z区间的连续字符，用到了花括号表明是一个集合。
scan "abcABC" {%[a-z]} res
=>1

puts $res
=>abc                # {} 表示一个字符串  %[a-z] 相当于正则表达式
                     # {%正则表达式}

scan "ABCabc" {%[A-b]} res
=>1
puts $res
=>ABCab

scan "ABCabc" {%[^a-b]} res   # ^是表示非的意思，%2[^a-b] 2个不是a-b
=>1
puts $res
=>ABC

scan "ABCabc" {%2[^a-b]} res
=>1
puts $res
=>AB

# 使用binary format对数值字符串25664进行二进制压缩，使用binary scan进行恢复
# 25664二进制数0110010001000000，需要使用两个字节进行存储
set b [binary format "s" 25664]            
=>@d                                  

puts $b
=>@d

binary scan $b "s" var 
=>1

puts $var
=>25664

binary scan 1 C var
=>1
puts $var
=>49

binary format spec value1?value...?
binary scan spec var1？var2.......?