Bash

The word “esac” is written at the end of the bash case statement that, tells the script to terminate the case statement. Read this article for more details.

In the bash script, the OR (||) is the logical operator examined for checking the conditions. It returns the results as “true” or “false.”

In the bash script, the data is written into the text file using the redirection operator (>, >>), tee command, or while loop.

In the Bash script, to check the number of passed arguments, use the special variable “$#” that holds the total number of passed arguments.

The string variables are compared in an“if” statement to check the equality/inequality of the strings using the “==” or “!=” operator.

In the bash script, to check whether the directory exists, utilize the “d” operator or “L” operator if the directory is symbolically linked.

The user can emulate the do-while loop in the bash script using the while loop syntax with “do”
that executes when the condition is true.

To fix the error “bad substitution” in the bash script, use the correct syntax, avoid repetition of characters and remove extra white spaces from the script.

The main reason for the error “mkvirtualenv: command not found” is that the virtual environment is not set. See the guide for more reasons and the solution.

To fix the error “integer expression expected,” use the correct bash syntax for integer and non-integer values. Read this post for more details on the error.

JSON scripting is not supported in shell scripting, but with the help of the jq command, it is made possible to the best extent. The curl command also helps.

In a Bash script, the “set -e” identifies the error location and exits the script execution quickly without the execution of other commands.

To extract file basename without path and extension, use the “basename” command. It can be done using the “parameter expansion” without the “basename.”

The string variables can be easily concatenated by “placing them sequentially” and using the “+=” operator in Bash shell scripts.

To change the dictionary in the current bash shell execute the script(bash) having the cd command with the “dot(.)” symbol and the “source” command.

Bash provides the “-v”, “-z”, and “-n” options to check whether the variable is set or not, at the conditional statement of the “if-then-else-fi” loop.

In Linux, the “grep” command allows the “-l(files-with-matches)” flag and the combination of the “find” command to show just filenames.

The “Ctrl-Z” key and the “&(ampersand)” symbol are different on the basis of their “objectives”, “usage”, “implementation” and “states”.

In Bash, the “<<<” operator means “here strings.” It allows users to pass a string as the standard input to a command via the “command <<< string” syntax.

To restart the Bash shell without restarting the terminal application, type the “exec bash” command that replaces the current process with the Bash shell.

In Bash, the hash table is the associative array which is defined using the declare command along with the “A” flag by specifying the array name.

There is no existence of a list data type in the bash script, but the list can be generated using the for and while loops or arrays.

The bash script has three boolean operators: AND, OR, and NOT. These operators have been discussed in detail in this article, along with examples.

Functions in bash scripting can help a user break down complex code in small portions, making it more manageable and simpler.

5 methods to convert a string to lowercase in bash Linux which are by using the “tr”, “awk”, and “sed” command, “bash string manipulation”, and “built-in function”.

A user can create a timestamp variable in the bash script using four different examples, which are date and printf command, logging script, and backup.

A user can exit the entire script using an “exit”, “return”, “kill”, and “killall” command if a certain condition occurs in the bash script.

To find the directory where the bash script is located, users can use the pwd, find, locate, and bash source command and the $0 variable.

A user can list only directories using the ls command using the -d, -F, and -l options in the bash script. Read this article for more detail.

The “2>&1” is a symbol that redirects error messages from standard error (stderr) to standard output (stdout). Read this article for more information.

The Purpose of “&&” in a Shell Command is to execute two commands simultaneously only if the first command is executed properly.

The Ternary Operator is a conditional operator that allows users to write conditional statements in a more concise and readable way.

Bash nested “for” loop contains the inner for loops that iterate entirely for each value of the outer for loop and execute the block of statements.

There are various ways to compare numbers in bash Linux, such as using if, nested if, or loops. These methods have been discussed along with examples.

To update the “.bashrc” file in Linux, open the “.bashrc” file with the nano editor, update the file, and reload it via the “source” command.

To perform calculations in bash the expression “(())” and “$(())” are used, the “$(())” returns the results while “(())” doesn’t and is applied on conditions.

In Linux, the bash shell variable “$$” returns the current bash shell process id that can be checked through the “echo” and the “ps(process)” commands.

To check if a variable exists in an if statement in bash scripting, the -v flag is used. However, checking a variable for a null or zero value -z flag is used.

The “Bash Indexed” array is a sequential arrangement of different types of elements associated with an “index,” a non-negative integer value.

Bash and shell scripting are similar, but bash is only executable in a bash shell, while shell script can be executed in any shell (bash, zsh, ksh, etc).

The “not equal” operator is the relational operator used to compare the two strings or the specified string. For more details, read this guide.

To convert the argument string to an integer using the “$((…))” arithmetic expansion operator, “expr,” “let,” “bc,” and “awk” commands in the bash script.

In Linux, the bash addition and multiplication operations can be performed using the “arithmetic expansion,” “expr,” and the “let” command line utility.

The “bash” and “sh” shells are different based on their “functionality,” “POSIX shell,” “programming language,” “compatibility,” and “command history.”

In the bash script file of Linux, the IFS is the field separator or token delimiter utilized in the string splitting. It is used for special escape characters.

In Linux, to make permanent aliases in the Zsh shell, the “.zshrc” file is utilized. Open this file with any editor, add the aliases, and execute it.

The #!/bin/sh and #/bin/bash are two different shell script interpreters. The system identifies the interpreter and then executes that script accordingly.

In Linux, use the “date”, “$SECONDS” internal bash variable, and the “TIMEFORMAT” string to get the execution time of the bash script.

If the command needs to be run in the same terminal session, then, yes the source command is necessary. If the session is refreshed, then no need to use it.

The “$?” variable holds the exit status of the last command executed by returning a value that confirms whether the script is executed or not.

In a Bash shell, $0 is a variable that represents the name of the current shell script. It displays the script name in the Command Line.

In Bash, the regular expression ‘^[0-9]+$’ matches a string that contains only one or more digits (0-9) and no other characters.

In the bash script, the seed value is defined in the “RANDOM” variable either manually or by the user input to generate the same number of sequences.

The purpose of the shift command shell script is to shift/move the positional arguments to the left that set each parameter to the lower position.

To create a permanent bash alias, edit the “~/.bashrc” file in Linux. After that, reload it using the “source ~/.bashrc” command to activate newly alias.

In bash scripting, the “if” loop is used to execute multiple conditional statements using “if-then fi”, and “if then else fi” and “if then else if fi” loop.

The “exit 0”, “exit 1”, and the “exit 2” returns the exit status of the bash shell script. The value of the exit command is stored in the “$(shell)” variable.

In Bash, the “declare” command sets the variable and functions alongside their attributes, “integer”, “string”, “array”, and “read-only” variables.

In Bash, the main difference between [email protected] and $* is that “[email protected]” preserves the individual arguments as separate words, while other preserves them as a single string.

In a bash script, the “set -x” activates the debugging feature at different places in the scripts or in the “bash shebang” line to identify the errors clearly.

To define the set of ranges in the for loop of the bash script, the “{#..#}” syntax is followed by the starting and the ending range.

In Bash, the “eval” command evaluates its arguments as a shell script including “commands”, “variables”, “arithmetic expressions”, and “strings”.

To implement the for each line operation on a file, the for loop is used in Bash scripting. This can be used to read each line of a file.

Learn to use the powerful Bash For Loop in your scripts. From basic usage to advanced examples, our guide covers everything you need to master the loop.

To make the shell script executable, grant the executable permissions to the file by using the command “chmod +x [filename].sh”.

Learn how to use the bash’s powerful “cat” command. Our comprehensive guide covers everything to make you master this command in no time!