1.0 Temporary Files Quite often, we need temporary files in our programs. Some intermediate data needs to be stored and the file can be discarded when the process terminates. There are multiple ways of creating temporary files in Linux. The best way to create a temporary file in Linux is to use the O_TMPFILE flag …
1.0 Error 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 … 2.0 Solution The error was resolved after adding the following iptables rules. iptables -I OUTPUT 1 -p udp -s 127.0.0.1 -d 127.0.0.1 -j …
1.0 last and lastb 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. Similarly, lastb, by default, reads the …
Find user login history – last and lastb commands in Linux Read More »
1.0 cut 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… [FILE]… You can cut out bytes, characters or fields from files. 2.0 Cut fields The …
1.0 tr 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. For example, to …
1.0 uniq 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. The input must be sorted for uniq to work correctly. For example, $ …
1.0 Sort 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 …
1.0 grep 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 …
1.0 Shell Script bash is the commonly used shell in GNU-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 shell script, or bash script, is a list of commands written to …
1.0 SHELL 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. A CLI shell is a programmable command interpreter …
