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Full Discussion: Function explanation
Top Forums UNIX for Beginners Questions & Answers Function explanation Post 303043530 by Chubler_XL on Thursday 30th of January 2020 04:47:52 PM
Old 01-30-2020
This function is quite well commented, it basically uses the tail command to print the last MAX_LENGTH ($2) lines of FILE ($1) these are stored in a temporary file (name generated by the mktmp command) the contents of this temporary file is then copied back over the original file and the temporary file removed.
All the operations performed are checked to ensure they have a success exit code before moving onto the next step.

Which particular part of the function you are having trouble understanding?
This User Gave Thanks to Chubler_XL For This Post:
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LEARN ABOUT CENTOS

systemd-tmpfiles-clean.service

SYSTEMD-TMPFILES(8)						 systemd-tmpfiles					       SYSTEMD-TMPFILES(8)

NAME

       systemd-tmpfiles, systemd-tmpfiles-setup.service, systemd-tmpfiles-setup-dev.service, systemd-tmpfiles-clean.service, systemd-tmpfiles-
       clean.timer - Creates, deletes and cleans up volatile and temporary files and directories

SYNOPSIS

       systemd-tmpfiles [OPTIONS...] [CONFIGFILE...]

       systemd-tmpfiles-setup.service

       systemd-tmpfiles-setup-dev.service

       systemd-tmpfiles-clean.service

       systemd-tmpfiles-clean.timer

DESCRIPTION

       systemd-tmpfiles creates, deletes, and cleans up volatile and temporary files and directories, based on the configuration file format and
       location specified in tmpfiles.d(5).

       If invoked with no arguments, it applies all directives from all configuration files. If one or more filenames are passed on the command
       line, only the directives in these files are applied. If only the basename of a configuration file is specified, all configuration
       directories as specified in tmpfiles.d(5) are searched for a matching file.

OPTIONS

       The following options are understood:

       --create
	   If this option is passed, all files and directories marked with f, F, w, d, D, p, L, c, b, m in the configuration files are created or
	   written to. Files and directories marked with z, Z, m have their ownership, access mode and security labels set.

       --clean
	   If this option is passed, all files and directories with an age parameter configured will be cleaned up.

       --remove
	   If this option is passed, all files and directories marked with r, R in the configuration files are removed.

       --boot
	   Also execute lines with an exclamation mark.

       --prefix=PATH
	   Only apply rules that apply to paths with the specified prefix. This option can be specified multiple times.

       --exclude-prefix=PATH
	   Ignore rules that apply to paths with the specified prefix. This option can be specified multiple times.

       --help
	   Prints a short help text and exits.

       It is possible to combine --create, --clean, and --remove in one invocation. For example, during boot the following command line is
       executed to ensure that all temporary and volatile directories are removed and created according to the configuration file:

	   systemd-tmpfiles --remove --create

EXIT STATUS

       On success, 0 is returned, a non-zero failure code otherwise.

SEE ALSO

       systemd(1), tmpfiles.d(5)

systemd 208														       SYSTEMD-TMPFILES(8)
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