'\" et
.TH STRINGS "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
strings
\(em find printable strings in files
.SH SYNOPSIS
.LP
.nf
strings \fB[\fR-a\fB] [\fR-t \fIformat\fB] [\fR-n \fInumber\fB] [\fIfile\fR...\fB]\fR
.fi
.SH DESCRIPTION
The
.IR strings
utility shall look for printable strings in regular files and shall
write those strings to standard output. A printable string is any
sequence of four (by default) or more printable characters terminated
by a
<newline>
or NUL character. Additional implementation-defined strings may be
written; see
.IR localedef .
.P
If the first argument is
.BR '\-' ,
the results are unspecified.
.SH OPTIONS
The
.IR strings
utility shall conform to the Base Definitions volume of POSIX.1\(hy2017,
.IR "Section 12.2" ", " "Utility Syntax Guidelines",
except for the unspecified usage of
.BR '\-' .
.P
The following options shall be supported:
.IP "\fB\-a\fP" 10
Scan files in their entirety. If
.BR \-a
is not specified, it is implementation-defined what portion of each
file is scanned for strings.
.IP "\fB\-n\ \fInumber\fR" 10
Specify the minimum string length, where the
.IR number
argument is a positive decimal integer. The default shall be 4.
.IP "\fB\-t\ \fIformat\fR" 10
Write each string preceded by its byte offset from the start of the
file. The format shall be dependent on the single character used as
the
.IR format
option-argument:
.RS 10 
.IP "\fRd\fR" 6
The offset shall be written in decimal.
.IP "\fRo\fR" 6
The offset shall be written in octal.
.IP "\fRx\fR" 6
The offset shall be written in hexadecimal.
.RE
.SH OPERANDS
The following operand shall be supported:
.IP "\fIfile\fR" 10
A pathname of a regular file to be used as input. If no
.IR file
operand is specified, the
.IR strings
utility shall read from the standard input.
.SH STDIN
See the INPUT FILES section.
.SH "INPUT FILES"
The input files named by the utility arguments or the standard input
shall be regular files of any format.
.SH "ENVIRONMENT VARIABLES"
The following environment variables shall affect the execution of
.IR strings :
.IP "\fILANG\fP" 10
Provide a default value for the internationalization variables that are
unset or null. (See the Base Definitions volume of POSIX.1\(hy2017,
.IR "Section 8.2" ", " "Internationalization Variables"
for the precedence of internationalization variables used to determine
the values of locale categories.)
.IP "\fILC_ALL\fP" 10
If set to a non-empty string value, override the values of all the
other internationalization variables.
.IP "\fILC_CTYPE\fP" 10
Determine 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 and input files) and to identify
printable strings.
.IP "\fILC_MESSAGES\fP" 10
.br
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard error.
.IP "\fINLSPATH\fP" 10
Determine the location of message catalogs for the processing of
.IR LC_MESSAGES .
.SH "ASYNCHRONOUS EVENTS"
Default.
.SH STDOUT
Strings found shall be written to the standard output, one per line.
.P
When the
.BR \-t
option is not specified, the format of the output shall be:
.sp
.RS 4
.nf

"%s", <\fIstring\fR>
.fi
.P
.RE
.P
With the
.BR "\-t\ o"
option, the format of the output shall be:
.sp
.RS 4
.nf

"%o %s", <\fIbyte offset\fR>, <\fIstring\fR>
.fi
.P
.RE
.P
With the
.BR "\-t\ x"
option, the format of the output shall be:
.sp
.RS 4
.nf

"%x %s", <\fIbyte offset\fR>, <\fIstring\fR>
.fi
.P
.RE
.P
With the
.BR "\-t\ d"
option, the format of the output shall be:
.sp
.RS 4
.nf

"%d %s", <\fIbyte offset\fR>, <\fIstring\fR>
.fi
.P
.RE
.SH STDERR
The standard error shall be used only for diagnostic messages.
.SH "OUTPUT FILES"
None.
.SH "EXTENDED DESCRIPTION"
None.
.SH "EXIT STATUS"
The following exit values shall be returned:
.IP "\00" 6
Successful completion.
.IP >0 6
An error occurred.
.SH "CONSEQUENCES OF ERRORS"
Default.
.LP
.IR "The following sections are informative."
.SH "APPLICATION USAGE"
By default the data area (as opposed to the text, ``bss'', or header
areas) of a binary executable file is scanned. Implementations
document which areas are scanned.
.P
Some historical implementations do not require NUL or
<newline>
terminators for strings to permit those languages that do not use NUL
as a string terminator to have their strings written.
.SH EXAMPLES
None.
.SH RATIONALE
Apart from rationalizing the option syntax and slight difficulties with
object and executable binary files,
.IR strings
is specified to match historical practice closely. The
.BR \-a
and
.BR \-n
options were introduced to replace the non-conforming
.BR \-
and
.BR \- \c
.IR number
options. These options are no longer specified by POSIX.1\(hy2008 but
may be present in some implementations.
.P
The
.BR \-o
option historically means different things on different
implementations. Some use it to mean ``\c
.IR offset
in decimal'', while others use it as ``\c
.IR offset
in octal''. Instead of trying to decide which way would be least
objectionable, the
.BR \-t
option was added. It was originally named
.BR \-O
to mean ``offset'', but was changed to
.BR \-t
to be consistent with
.IR od .
.P
The ISO\ C standard function
\fIisprint\fR()
is restricted to a domain of
.BR "unsigned char" .
This volume of POSIX.1\(hy2017 requires implementations to write strings as defined by the
current locale.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIlocaledef\fR\^",
.IR "\fInm\fR\^"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "Chapter 8" ", " "Environment Variables",
.IR "Section 12.2" ", " "Utility Syntax Guidelines"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .