While executing the dig command, the sendmsg() failed: Operation not permitted
error was printed.
$ dig example.com ../../../../lib/isc/unix/net.c:581: sendmsg() failed: Operation not permitted ../../../../lib/isc/unix/net.c:581: sendmsg() failed: Operation not permitted ...
The error was resolved after adding the following iptables rules.… Read more “Error while executing the dig command”
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 “Find user login history – last and lastb commands in Linux”
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 “Cut command in Linux”
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 “tr Command in Linux”
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 “Uniq command in Linux”
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 “Sort command in Linux”
grep is a program for searching a given string pattern in files. It searches the files for the pattern and prints the lines that contain strings matching the pattern. For example,
$ # grep pattern filenames ...
$ grep 'hbox' find.c
GtkWidget *window, *scrolled_win, *hbox, *vbox, *find;
hbox = gtk_hbox_new (FALSE, 5);
gtk_box_pack_start (GTK_BOX (hbox), w -entry, TRUE, TRUE, 0);
gtk_box_pack_start (GTK_BOX (hbox), find, FALSE, TRUE, 0);
gtk_box_pack_start (GTK_BOX (vbox), hbox, FALSE, TRUE, 0);
grep [OPTIONS] pattern [file ...] grep [OPTIONS] [-e pattern | -f file ] [file ...]
The pattern, mentioned above, is a regular expression.… Read more “grep Command in Linux”
bash can be run interactively, as a login shell or as an interactive process from a terminal emulator like the gnome-terminal. bash can be run non-interactively by running a bash script. A bash script is a list of commands written to automate some system operations work in Linux.… Read more “Bash Scripting Tutorial”
A shell provides a user interface to a computer system. There are two types of shells, the command line interface (CLI) and the graphical user interface (GUI). In this tutorial, we describe the command line interface shell only and refer to it simply as shell
.… Read more “Bash Tutorial”
The ss command gives the socket statistics. It gives information about the network connections. ss is a replacement for the netstat command.
By default, the ss command gives information about non-listening sockets.
$ ss Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port u_str ESTAB 0 0 * 4482 * 4481 u_str ESTAB 0 0 * 4285 * 3631 ...… Read more “ss command in Linux”