read(1) manual page
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read - read a line from standard input
/usr/bin/read
[-r] var ...
read name ...
set variable = $<
read [ -prsu[ n ] ] [ name?prompt
] [ name ... ]
SUNWcsu
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.
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.
The notation
set variable = $<
loads one line of standard input as the value for variable. (See csh(1)
).
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.
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.
The following operand is supported:
- var
- The name of an existing
or non-existing shell variable.
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
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.
The following exit values are returned:
- Successful completion.
- >0
- End-of-file was detected or an error occurred.
csh(1)
, ksh(1)
, line(1)
, set(1)
, sh(1)
, environ(5)
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