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.
ulimit — set or report file size limit
ulimit [−f] [blocks]
The ulimit utility shall set or report the file-size writing limit imposed on files written by the shell and its child processes (files of any size may be read). Only a process with appropriate privileges can increase the limit.
The ulimit utility shall conform to the Base Definitions volume of POSIX.1-2008, Section 12.2, Utility Syntax Guidelines.
The following option shall be supported:
Set (or report, if no blocks operand is present), the file size limit in blocks. The −f option shall also be the default case.
The following operand shall be supported:
The number of 512-byte blocks to use as the new file size limit.
The following environment variables shall affect the execution of ulimit:
Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.1-2008, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)
If set to a non-empty string value, override the values of all the other internationalization variables.
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).
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
Determine the location of message catalogs for the processing of LC_MESSAGES.
The standard output shall be used when no blocks operand is present. If the current number of blocks is limited, the number of blocks in the current limit shall be written in the following format:
"%d\n", <number of 512-byte blocks>
If there is no current limit on the number of blocks, in the POSIX locale the following format shall be used:
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
A request for a higher limit was rejected or an error occurred.
The following sections are informative.
Since ulimit affects the current shell execution environment, it is always provided as a shell regular built-in. If it is called in a separate utility execution environment, such as one of the following:
env ulimit 10000
it does not affect the file size limit of the caller’s environment.
Once a limit has been decreased by a process, it cannot be increased (unless appropriate privileges are involved), even back to the original system limit.
Set the file size limit to 51200 bytes:
ulimit −f 100
The Base Definitions volume of POSIX.1-2008, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines
The System Interfaces volume of POSIX.1-2008, ulimit()
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
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