Infinite-File-Curtailer - a program that reads stdin and writes to a fixed size file.

Requires Linux 3.15+ and a filesystem that supports the FALLOC_FL_COLLAPSE_RANGE flag for fallocate. This is currently ext4 and XFS. Hopefully more in the future...

Usage

./curtail [-s size] <output file>

Options:

-verbose  enable all debug output (on stderr)
-quiet    disable all non-error output (on stderr)
-size     Maximum size of the output file (ie. 8192, 64K, 10M, 1G, etc) - default is 16K

Example

A typical usage scenario is to capture the output of a program in a file. Using curtail prevents the program from creating a runaway file that will eventually fill up the filesystem and cause system failure if not handled at the system level. In the example below, the file my_app_log.txt cannot exceed 2 megabytes in size.

./my_app | curtail -s 2M ./my_app_log.txt

Build instructions

Curtail uses autotools (must be installed on the local system). To build curtail locally, please run the following commands from the base dir of the project:

libtoolize
aclocal
autoheader
autoconf
automake
./configure
make

To install in the local system, run the following additional command with appropriate priviledges:

make install

Library usage

Curtail can also be integrated directly into an application instead of used on the command line. Include the file curtail.h and link the application with -lcurtail. After successfully calling crtl_init, the program's stdout will be directed to the specified file until crtl_term is called.

Logrotate comparision

Curtail is not intended to be a replacement for logrotate. They are fundamentally different. Some of the notable differences are below:

logrotate mitigates runaway files... curtail prevents them.
logrotate requires sysadmin... curtail does not. logrotate creates multiple files... curtail only one.