Module 74 line (SV) | Illustrated Unix System V/Bsd

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Module 74
line (SV)

DESCRIPTION

The external line command is used to read if a line of input and write it to the standard output. The standard input is usually your keyboard and the standard output is your terminal screen. It always writes a new-line to the standard output. If it reads at end-of-file it returns af exit status of 1.

NOTE:
Something to remember about the line command: you can only read in a line of text to one variable. The read command can assign each word on the input to a different variable. This problem can be resolved using the set command.

COMMAND FORMAT

Following is the general format of the line command.

 line

RELATED COMMANDS

Refer to the echo , print , and read commands described if modules 38, 106, and 112.

RELATED FILES

The line command reads from the standard input and writes to the standard output.

RETURN CODES

A return code of 1 is returned if an EOF(Ctrl-D) is encountered .

APPLICATIONS

The line command is usually used in shell scripts to read in a line of input and assign it to a variable. To do this you must enclose the line command in grave accents to perform command substitution.

NOTE:
The line command was a substitute command for the shell read command before System V Release 2.0. The old read command was hardcoded to read from your keyboard. It read from your keyboard evem if the input had been redirected from a file. Thus line filled a need to read from the standard input even if it had been redirected.

TYPICAL OPERATION

In this activity you use the line command to read in a line of input and store it in a variable. Begin at the shell prompt.

1. Type INLINE= ˜line ˜ and press Return . Notice your shell prompt did not return.

2. Now type Input line to the line command! and press Return . The text you typed is stored in the variable named INLINE.

3. To display the contents of INLINE type echo $INLINE and press Return . The one problem with the line command is the assignment of values to variables . Only one variable can be used and it must contain all of the contents read by line .

4. Turn to Module 112 to continue the learning sequence.

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