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1. Top results related to what should a shell script programmer know about linux os

   • What does "read -p" do in a linux shell script?

     Top Answer

     Answered Apr 13, 2017 · 19 votes

     First off, the structure <command> -<option> means that you want to execute <command> using the option corresponding to <option>. A - after a command means that the following letter is an option. Most commands have several options you can use. Options are usually defined using either a single letter or a couple of words separated by -.

     Side Note: For options that are a couple of words rather than a single letter, often it will use two minus signs -- instead of one, signifying that it is a "long named" option.

     So, using the read -p example, this means you want to execute read using the p option, which stands for prompt.

     Now, sometimes an option will require an argument. In your examples, the options to useradd have arguments. Arguments are usually defined like <command> -<option> [argument]. So, in the useradd example, $group is an argument for the option g.

     Now for the commands themselves:

     read

     is a bash built-in (not a POSIX shell command) that reads from standard input.

     • The -p option makes it read as a prompt, meaning it doesn't add a trailing newline before trying to read input.

     if

     checks the return status of the test command (in this case id -u $username >/dev/null 2>&1)

     • If the return status is 0, the then part is executed

     id

     prints user groups and ids

     • The -u option "prints only the effective user ID".
     • >/dev/null 2>&1 redirects standard input and standard error to /dev/null, meaning they do not get printed to the terminal.

     useradd

     creates a new user

     • -g sets the initial group for the user
     • -s sets the name of the user's login shell
     • -d sets the name of the user's login directory
     • -m says to create the user's home directory if it does not exist.
     • -p defines the user's encrypted password.

     For future reference, you can look up commands in the linux manual pages by doing man <command> on the command line. These manual pages tell you what a command does, as well as explaining all of its options.

     Bash built-ins like read are all on a single man page that is not the easiest thing to use. For those I find googling them easier. Usually http://ss64.com/ will come up in the results, which contains the info from the bash built-ins man page, but separated into different pages by command. I find this much easier to use.

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     1/5

   • Linux shell script to know if the directory (or file) has 777 permission

     Top Answer

     Answered Jul 03, 2021 · 4 votes

     You don't need to process the output of stat with grep; you can ask stat to only produce the specific information you want. See the man page regarding the --format option. We can for example write:

     # ask stat for the file type and mode, and put those values into $1# and $2set -- $(stat --format '%F %a' /Temp)if [[ $1 == directory ]]; then if [[ $2 == 777 ]]; then echo "/Temp folder has full access" else sudo chmod -R 777 /Temp fielse echo "ERROR: /Temp is not a directory!" >&2fi

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     2/5

   • Linux shell script to copy last lines of a file in a directory to append to a file in another directory

     Top Answer

     Answered Oct 10, 2014 · 0 votes

     `"tail -"$Lines1"f /opt/grinder/svn/IAVS/GrinderLogs/GrinderBaseLogs/Lg2Logs/"$GrinderLg2"-"$c"-data.log>>/opt/grinder/svn/IAVS/GrinderLogs/GrinderBaseLogs/"$GrinderLG1"-"$c"-data.log"`-

     change to

     tail -"$Lines1"f /opt/grinder/svn/IAVS/GrinderLogs/GrinderBaseLogs/Lg2Logs/"$GrinderLg2"-"$c"-data.log>>/opt/grinder/svn/IAVS/GrinderLogs/GrinderBaseLogs/"$GrinderLG1"-"$c"-data.log-

     should work.

     In my setup i have tested as below way

     #!/bin/sh`"tail -10f filename"`-

     give error filename not found

     But

     #!/bin/shtail -10f filename-

     This works fine.

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     3/5

   • A shell script to run a process on linux

     Top Answer

     Answered Mar 30, 2014 · 0 votes

     #!/bin/bash-APP="xmldiff"A="folder path"B="folder path"result="folder path"# This function extract the basename /path/to/basename.ext -> basenamegetBaseName(){local name="$1"basename=`echo "$name" | sed -r -e "s/.+\/([^\/]+)\.[^\.]+$/\1/"`echo "$basename"}for _file in $A/*do filename=`getBaseName "$_file"`# I'm assuming here that you have only xml files ending in .xml"$APP" "$A/${filename}.xml" "$B/${filename}.xml" "$result/${filename}_result.xml"done

     NOTE: Copy this in a new text file. Then from cmdline type : chmod +x yourfilename. To exec from same folder : ./yourfilename

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     4/5

   • Linux Shell script what dirname and ? means?

     Top Answer

     Answered Dec 05, 2013 · 5 votes

     The dirname command removes the trailing / component from the NAME and prints the remaining portion. If the NAME does not contain / component then it prints '.' (means current directory)

     Dirname Command Example:

     Remove the file name from absolute path.

     Let say my directory path is /usr/local/bin/add.sh. Now i want to remove /add.sh and display only /usr/local/bin, then we can use the dirname command.

     dirname /usr/local/bin/add.sh/usr/local/bin

     NAME

     dirname - strip non-directory suffix from file name

     SYNOPSIS

     dirname NAME dirname OPTION

     DESCRIPTION

     Print NAME with its trailing /component removed; if NAME contains no /’s, output ‘.’ (meaning the current directory).

     Edit: Also, Some characters have special functions in linux commands ? <-- Matches one character

     Source

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     5/5

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2. www.geeksforgeeks.org › introduction-linux-shellIntroduction to Linux Shell and Shell Scripting - GeeksforGeeks

   www.geeksforgeeks.org › introduction-linux-shell

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   Apr 16, 2024 · A shell script comprises the following elements – Shell Keywords – if, else, break etc. Shell commands – cd, ls, echo, pwd, touch etc. Functions; Control flow – if..then..else, case and shell loops etc. Why do we need shell scripts? There are many reasons to write shell scripts: To avoid repetitive work and automation

3. www.freecodecamp.org › news › shell-scripting-crashShell Scripting for Beginners – How to Write Bash Scripts in ...

   www.freecodecamp.org › news › shell-scripting-crash

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   Mar 31, 2022 · The basic syntax of shell scripting. How to see a system's scheduled scripts. How to automate scripts by scheduling via cron jobs. The best way to learn is by practicing. I highly encourage you to follow along using Replit. You can access a running Linux shell within minutes. Introduction to the Bash Shell

4. People also ask

   What is shell scripting in Linux?

   • Shell scripting is an important part of process automation in Linux. Scripting helps you write a sequence of commands in a file and then execute them. This saves you time because you don't have to write certain commands again and again. You can perform daily tasks efficiently and even schedule them for automatic execution.

   Shell Scripting for Beginners – How to Write Bash Scripts in Linux

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   What is Bash shell programming?

   • This guide is an introduction to bash shell programming. Bash shell programming empowers Linux users to take programmatic control over the Linux operating system. The bash shell provides a number of concepts common to many other programming languages, so if you know another language then you should be able to pick up bash with relative ease.

   Introduction to Bash Shell Scripting | Linode Docs

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   What will I learn in a shell scripting course?

   • You’ll create simple to more advanced shell scripts that involve Metacharacters, Quoting, Variables, Command substitution, I/O Redirection, Pipes & Filters, and Command line arguments. You will also schedule cron jobs using crontab. The course includes both video-based lectures as well as hands-on labs to practice and apply what you learn.

   Hands-on Introduction to Linux Commands and Shell Scripting - Course…

   www.coursera.org/learn/hands-on-introduction-to-linux-commands-and-shell-scripting

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   What is shell in Linux?

   • Shell accepts human-readable commands from users and converts them into something which the kernel can understand. It is a command language interpreter that executes commands read from input devices such as keyboards or from files. The shell gets started when the user logs in or starts the terminal. Shell is broadly classified into two categories –

   Introduction to Linux Shell and Shell Scripting - GeeksforGeeks

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5. www.freecodecamp.org › news › bash-scriptingBash Scripting Tutorial – Linux Shell Script and Command Line ...

   www.freecodecamp.org › news › bash-scripting

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   Mar 20, 2023 · Get started. In Linux, process automation relies heavily on shell scripting. This involves creating a file containing a series of commands that can be executed together. In this article, we'll start with the basics of bash scripting which includes variables, commands, inputs/ outputs, and debugging.

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6. www.howtogeek.com › 67469 › the-beginners-guide-toThe Beginner's Guide to Shell Scripting: The Basics - How-To Geek

   www.howtogeek.com › 67469 › the-beginners-guide-to

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   Shell scripts allow us to program commands in chains and have the system execute them as a scripted event, just like batch files. They also allow for far more useful functions, such as command substitution. You can invoke a command, like date, and use it's output as part of a file-naming scheme.

7. medium.com › sysf › bash-scripting-everything-youBash Scripting: Everything you need to know about Bash-shell ...

   medium.com › sysf › bash-scripting-everything-you

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   A shell scripting is writing a program for the shell to execute and a shell script is a file or program that shell will execute. If you are a programmer, then you might...

8. www.linode.com › guides › intro-bash-shell-scriptingIntroduction to Bash Shell Scripting | Linode Docs

   www.linode.com › guides › intro-bash-shell-scripting

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   Sep 27, 2019 · Bash shell programming empowers Linux users to take programmatic control over the Linux operating system. The bash shell provides a number of concepts common to many other programming languages, so if you know another language then you should be able to pick up bash with relative ease. In This Guide. Among other things, you will learn about:

9. www.coursera.org › learn › hands-on-introduction-toHands-on Introduction to Linux Commands and Shell Scripting

   www.coursera.org › learn › hands-on-introduction-to

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   Develop shell scripts using Linux commands, environment variables, pipes, and filters. Schedule cron jobs in Linux with crontab and explain the cron syntax. Skills you'll gain. Shell Script. Bash (Unix Shell) Extract Transform and Load (ETL) Linux Commands. Details to know. Shareable certificate. Add to your LinkedIn profile. Assessments.