9.19. Printing the Values of Variables in the TC Shell

9.19.1 The echo Command

The built-in echo command prints its arguments to standard output. The echo allows the use of numerous escape sequences that are interpreted and displayed as tabs, newlines, form feed, and so on. Table 9.21 lists the echo options and escape sequences.

Table 9.21. echo Options and Escape Sequences

Option	Meaning
-n	Suppresses newline at the end of a line of output
Escape Sequences
\a	Alert (bell)
\b	Backspace
\c	Print the line without a newline
\f	Form feed
\n	Newline
\r	Return
\t	Tab
\v	Vertical tab
\\	Backslash
\nnn	The character whose ASCII code is nnn (octal)

The TC shell uses the style of both BSD and SVR4, but allows you to modify the behavior of the echo command by using the built-in echo_style variable; for example, set echo_style=bsd. See Table 9.22, and the manual page for echo.

Table 9.22. The echo_style Variable (SVR4 and BSD)

System	Behavior
bsd	If the first argument is -n, the newline is suppressed
both	Both -n and escape sequences are in effect (the default)
none	Recognizes neither sysv or bsd
sysv	Expands escape sequences in echo strings

Example 9.101.

1   > echo The username is $LOGNAME.

    The username is ellie.

2   > echo "\t\tHello there\c"

                Hello there>

3   > echo -n "Hello there"

    Hello there$

4   > set echo_style=none

5   > echo  "\t\tHello there\c"

    -n \t\tHello there\c

EXPLANATION

9.19.2 The printf Command

The GNU version of printf can be used to format printed output. It prints the formatted string, in the same way as the C printf function. The format consists of a string that may contain formatting instructions to describe how the printed output will look. The formatting instructions are designated with a % followed by specifiers (diouxXfeEgGcs), where %f would represent a floating-point number and %d would represent a whole (decimal) number.

To see a complete listing of printf specifiers and how to use them, type at the command-line prompt printf – –help. (See Table 9.23.) To see what version of printf you are using, type printf – –version.

Table 9.23. Format Specifiers for the printf Command

Format Specifier	Value
\"	Double quote
\0NNN	An octal character in which NNN represents 0 to 3 digits
\\	Backslash
\a	Alert or beep
\b	Backspace
\c	Produce no further output
\f	Form feed
\n	Newline
\r	Carriage return
\t	Horizontal tab
\v	Vertical tab
\xNNN	Hexadecimal character in which NNN is 1 to 3 digits
%%	Single %
%b	ARGUMENT as a string with \ escapes interpreted

FORMAT

printf format [argument...]

Example 9.102.

printf "%10.2f%5d\n" 10.5  25

Example 9.103.

1   > printf --version

    printf (GNU sh-utils) 1.16

2   > printf "The number is %.2f\n" 100

    The number is 100.00

3   > printf "%-20s%-15s%10.2f\n" "Jody" "Savage" 28

    Jody                Savage              28.00

4   > printf "|%-20s|%-15s|%10.2f|\n" "Jody" "Savage" 28

    |Jody                |Savage         |     28.00|

EXPLANATION

9.19.3 Curly Braces and Variables

Curly braces insulate a variable from any characters that may follow it. They can be used to concatenate a string to the end of the variable.

Example 9.104.

1   > set var = net

    > echo $var

    net

2   > echo $varwork

    varwork: Undefined variable.

3   > echo ${var}work

    network

EXPLANATION

9.19.4 Uppercase and Lowercase Modifiers

A special history modifier can be used to change the case of letters in a variable.

Table 9.24. TC Shell Case Modifiers

Modifier	What It Does
:a	Apply a modifier as many times as possible to a single word.
:g	Apply a modifier once to each word.
:l	Lowercase the first uppercase letter in a word.
:u	Uppercase the first lowercase letter in a word.

Example 9.105.

1   > set name = nicky

    > echo $name:u

    Nicky

2   > set name = ( nicky jake )

    > echo $name:gu

    Nicky Jake

3   > echo $name:agu

    NICKY JAKE

4   > set name = ( TOMMY DANNY )

    > echo $name:agl

    tommy danny

5   > set name = "$name:agu"

    > echo $name

    TOMMY DANNY

EXPLANATION