Newly Released LPI 102-500 Exam PDF

The test command is used to perform checks and comparisons on files and values. The -e option tests if a given path exists, regardless of its type (file, directory, link, etc.). The -f option tests if a given path exists and is a regular file, not a directory or a special file. For example, if we have a directory named dir and a file named file, we can use the test command as follows:

test -e dir && echo “dir exists” dir exists test -f dir && echo “dir is a regular file” (no output) test -e file && echo “file exists” file exists test -f file && echo “file is a regular file” file is a regular file

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The command that allows you to make a shell variable visible to subshells is export VARIABLE. This command turns the variable into a global or environment variable, which means it can be accessed by any child process or subshell that inherits the environment of the parent shell. The syntax of the export command does not require a dollar sign ($) before the variable name, unlike when referencing the value of the variable. The other commands are either invalid or do not affect the visibility of the variable to subshells. The set command can be used to assign values to variables, but it does not export them. The env command can be used to run a command in a modified environment, but it does not change the environment of the current shell. References:

[LPI Linux Essentials - Topic 105: Shells, Scripting and Data Management]

[LPI Linux Professional - Exam 102 Objectives - Topic 105: Shells and Shell Scripting]

What is a Subshell? - Linux Bash Shell Scripting Tutorial Wiki - nixCraft

What is Subshell in Linux? [Explained]

The seq command in Linux is used to generate a sequence of numbers from FIRST to LAST in steps of INCREMENT1. The syntax for the seq command is:

seq [OPTION]… LAST or seq [OPTION]… FIRST LAST or seq [OPTION]… FIRST INCREMENT LAST

In this case, the command seq 1 5 20 has three arguments: FIRST = 1, INCREMENT = 5, and LAST = 20. This means that the command will produce numbers from 1 to 20 in steps of 5. The output will be:

1 5 10 15

The output will not include 20 because it is not a multiple of 5. The output will be printed on separate lines by default, unless a different separator is specified with the -s option2. References:

Seq Command in Linux [Explained With Examples]

seq Man Page - Linux - SS64.com - SS64 Command line reference

 The alias command is used to create, list, or remove aliases in the current shell. An alias is a short name that refers to another command, usually with some options or arguments. Aliases are useful for saving typing time, avoiding spelling errors, or customizing the behavior of commands. To list all the aliases defined in the current shell, we can use the alias command without any arguments. This will print the aliases in the format of alias name='command'123. For example:

$ alias alias cp=‘cp -i’ alias l=‘ls -CF’ alias la=‘ls -A’ alias ll=‘ls -alF’ alias mv=‘mv -i’ alias rm=‘rm -i’

The output shows that some common commands, such as cp, mv, and rm, have aliases that add the -i option, which prompts the user before overwriting or deleting files. The l, la, and ll aliases are shortcuts for different variations of the ls command, which lists files and directories123.

References: 1: List All Available Commands and Aliases in Linux - Baeldung 2: get all aliases in linux shell - Stack Overflow 3: How to list all aliases on Linux - Linux Tutorials - Learn Linux Configuration