read - Reads a line from standard input
read [-r] var...
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-r Do not treat a backslash character in any special way. Consider each
backslash to be part of the input line.
The -r option is included to enable read to subsume the purpose of
the obsolete line utility.
var The name of an existing or non-existing shell variable.
The read utility reads 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 prompts for a continuation line in the following
+ 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
The line is split into fields as in the shell (see the sh(1) reference
page); the first field is assigned to the first variable var, the second
field to the second variable var, and so forth. If there are fewer var
parameters specified than there are fields, the leftover fields and their
intervening separators are assigned to the last var. If there are fewer
fields than vars, the remaining vars are set to empty strings.
The setting of variables specified by the var parameters affects the
current shell execution environment. If read is called in a subshell or
separate utility execution environment, such as one of the following, it
does not affect the shell variables in the caller's environment:
nohup read ...
find . -exec read ... \;
The -r option is included to enable read to subsume the purpose of the
obsolete line utility.
The results are undefined if an end-of-file is detected following a
backslash at the end of a line when -r is not specified.
The following exit values are returned:
0 Successful completion.
>>0 End-of-file was detected or an error occurred.
The following command prints a file with the first field of each line moved
to the end of the line:
while read -r xx yy
printf "%s %s\n" "$yy" "$xx"
done < input_file
The following environment variables affect the execution of read:
IFS Determines the internal field separators used to delimit fields.
Provides a default value for the internationalization variables that
are unset or null. If LANG is unset or null, the corresponding value
from the default locale is used. If any of the internationalization
variables contain an invalid setting, the utility behaves as if none of
the variables had been defined.
If set to a non-empty string value, overrides the values of all the
other internationalization variables.
Determines the locale for the interpretation of sequences of bytes of
text data as characters (for example, single-byte as opposed to multi-
byte characters in arguments).
Determines the locale used to affect the format and contents of diag-
nostic messages written to standard error.
Determines the location of message catalogues for the processing of
PS2 Provides 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.