systemd is the newer init system used in most Linux distributions since 2015. The first widely used init system was the System V init process, sysvinit. Ubuntu introduced the Upstart init system with Ubuntu 6.10 in 2006. Ubuntu fully migrated to systemd with Ubuntu 15.04 in 2015.… Read more
Syslog is a protocol for conveying event notification messages.
Syslog was first developed by Eric Allman for logging as a part of the Sendmail project in the 1980s. It soon became a de-facto standard for logging on Unix-like systems.… Read more
The last command gives a chronological list of user logins in a Linux system for a period of time. The lastb commands gives a similar list of failed logins to the system. By default, last uses the /var/log/wtmp file for the record of login data.… Read more
tmpfs is a filesystem that resides in the main memory of a Linux system. In the case of disk files, a file is first fetched into the kernel pagecache and the delivered to the requesting process. The fetch part is not there in the case of tmpfs as the files are created and updated directly in kernel caches.… Read more
The cut command cuts sections of each line of input files and writes it on its standard output. It is mostly used for taking out a few columns from the input files. The command syntax is,
cut option...… Read more
The tr command is a filter which reads the standard input, translates or deletes characters and writes on its standard output. The tr command syntax is,
tr [OPTION]... SET1 [SET2]
tr transliterates characters from SET1 into corresponding characters of SET2 in input and writes resulting text on the standard output.… Read more
The comm command compares two sorted files and gives output in three columns. The first column has lines which are present only in the first file. The second column contains lines which are present only in the second file.… Read more
The uniq command is a filter for finding unique lines in input. It reads input, suppresses duplicates and prints unique lines in its output. Used with the -D option, we can do the inverse and print the duplicate lines only.… Read more
The sort command is for sorting lines in text files. For example, if we have a file names, we can sort it with the sort command,
$ cat names John Doe Jane Doe John Roe Richard Roe Tommy Atkins Max Mustermann Erika Mustermann Joe Bloggs $ $ sort names Erika Mustermann Jane Doe Joe Bloggs John Doe John Roe Max Mustermann Richard Roe Tommy Atkins
The words in the input lines are fields, which are numbered 1 onwards.… Read more
awk is a filter which takes the input and gives output after matching desired patterns and doing processing linked to matched patterns. awk is well suited for processing voluminous raw text data and producing statistical reports from it.
awk is named after the first character of the names of its designers, Al Aho, Peter Weinberger and Brian Kernighan, who developed it for Unix systems in the 1970s.… Read more
