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Manual page for read(1)

read - read a line from standard input

SYNOPSIS

/usr/bin/read [-r] var ...

sh

read name ...

csh

set variable = $<

ksh

read [ -prsu[ n ] ] [ name?prompt ] [ name ... ]

DESCRIPTION

/usr/bin/read

The read utility will read a single line from standard input.

By default, unless the -r option is specified, backslash (\) acts as an escape character. If standard input is a terminal device and the invoking shell is interactive, read will prompt for a continuation line when:

The shell reads an input line ending with a backslash, unless the -r option is specified.
A here-document is not terminated after a newline character is entered.

The line will be split into fields as in the shell; the first field will be assigned to the first variable var, the second field to the second variable var, and so forth. If there are fewer var operands specified than there are fields, the leftover fields and their intervening separators will be assigned to the last var. If there are fewer fields than vars, the remaining vars will be set to empty strings.

The setting of variables specified by the var operands will affect the current shell execution environment. If it is called in a subshell or separate utility execution environment, such as one of the following:

(read foo)
nohup read ...
find . -exec read ... \;

it will not affect the shell variables in the caller's environment.

The standard input must be a text file.

sh

One line is read from the standard input and, using the internal field separator, IFS (normally space or tab), to delimit word boundaries, the first word is assigned to the first name, the second word to the second name, etc., with leftover words assigned to the last name. Lines can be continued using \newline. Characters other than newline can be quoted by preceding them with a backslash. These backslashes are removed before words are assigned to names, and no interpretation is done on the character that follows the backslash. The return code is 0, unless an EOF is encountered.

csh

The notation
set variable = $<
loads one line of standard input as the value for variable. (See csh.1

ksh

The shell input mechanism. One line is read and is broken up into fields using the characters in IFS as separators. The escape character, (\), is used to remove any special meaning for the next character and for line continuation. In raw mode, -r, the \ character is not treated specially. The first field is assigned to the first name, the second field to the second name, etc., with leftover fields assigned to the last name. The -p option causes the input line to be taken from the input pipe of a process spawned by the shell using |&. If the -s flag is present, the input will be saved as a command in the history file. The flag -u can be used to specify a one digit file descriptor unit n to read from. The file descriptor can be opened with the exec special command. The default value of n is 0. If name is omitted then REPLY is used as the default name. The exit status is 0 unless the input file is not open for reading or an end-of-file is encountered. An end-of-file with the -p option causes cleanup for this process so that another can be spawned. If the first argument contains a ?, the remainder of this word is used as a prompt on standard error when the shell is interactive. The exit status is 0 unless an end-of-file is encountered.

OPTIONS

The following option is supported:

-r: Do not treat a backslash character in any special way. Consider each backslash to be part of the input line.

OPERANDS

The following operand is supported:

var: The name of an existing or non-existing shell variable.

EXAMPLES

The following example for /usr/bin/read prints a file with the first field of each line moved to the end of the line.

while read -r xx yy
do
	printf "%s %s\n" "$yy" "$xx"
done < input_file

ENVIRONMENT

See environ.5 for descriptions of the following environment variables that affect the execution of read: LC_CTYPE, LC_MESSAGES, and NLSPATH.

IFS: Determine the internal field separators used to delimit fields.
PS2: Provide the prompt string that an interactive shell will write to standard error when a line ending with a backslash is read and the -r option was not specified, or if a here-document is not terminated after a newline character is entered.

EXIT STATUS

The following exit values are returned:

0: Successful completion.
>0: End-of-file was detected or an error occurred.