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The Command-Line Prompt

Syntax of a Shell Command

Case Sensitive

# Lists what is in the current location.
[arcc-t05@blog1 ~]$ ls
Desktop  Documents  Downloads
# Throws an error.
[arcc-t05@blog1 ~]$ LS
-bash: LS: command not found
Filename  ≠  FiLeNaMe  ≠  FILENAME

Filename  ≠  FiLeNaMe  ≠  FILENAME

Getting Help: man

[arcc-t05@blog1 ~]$ man ls
LS(1)                                     User Commands                                     LS(1)
NAME
       ls - list directory contents
SYNOPSIS
       ls [OPTION]... [FILE]...
DESCRIPTION
       List  information about the FILEs (the current directory by default).  Sort entries alpha‐
       betically if none of -cftuvSUX nor --sort is specified.
       Mandatory arguments to long options are mandatory for short options too.
       -a, --all
              do not ignore entries starting with .
       -A, --almost-all
              do not list implied . and ..
       ...
Manual page ls(1) line 1 (press h for help or q to quit)

Getting Help: <command --help>

[arcc-t05@blog1 ~]$ ls --help
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.
Mandatory arguments to long options are mandatory for short options too.
  -a, --all                  do not ignore entries starting with .
  -A, --almost-all           do not list implied . and ..
      --author               with -l, print the author of each file
  -b, --escape               print C-style escapes for nongraphic characters
      --block-size=SIZE      with -l, scale sizes by SIZE when printing them;
                               e.g., '--block-size=M'; see SIZE format below
  -B, --ignore-backups       do not list implied entries ending with ~

Getting Help: Options

Typically, options can have a:

short-name: “-a”:
- Single letter following a single “-”
long-name: “--all”:
- More descriptive word after two dashes “--”

Short options can be grouped:

“ls -a –l” can be shortened to “ls –al”

Single vs Multiple Lines

[arcc-t05@blog1 ~]$ ls -al ~
[arcc-t05@blog1 ~]$ ls \
> -al \
> ~

Exercises

Questions:

Is there a difference between running ls versus ls -al?
How can you find out what the –al options do?
What does the pwd command do?
From the command line, what happens if you press the up/down arrow keys?

Answers(1)

1: Is there a difference between running ls versus ls -al?

[arcc-t05@blog1 ~]$ ls
Desktop  Documents  Downloads
[arcc-t05@blog1 ~]$ ls -al
total 76
drwxr-x---   8 arcc-t05 arcc-t05  4096 Oct  3 13:57 .
drwxr-xr-x 925 root     root     32768 Sep 27 16:21 ..
-rw-------   1 arcc-t05 arcc-t05   212 Sep 12 15:44 .bash_history
-rw-r--r--   1 arcc-t05 arcc-t05    18 Aug 10 17:00 .bash_logout
-rw-r--r--   1 arcc-t05 arcc-t05   141 Aug 10 17:00 .bash_profile
-rw-r--r--   1 arcc-t05 arcc-t05   376 Aug 10 17:00 .bashrc
drwx------   3 arcc-t05 arcc-t05  4096 Sep 12 11:36 .config
drwxr-xr-x   2 arcc-t05 arcc-t05  4096 Aug 10 17:00 Desktop
drwxr-xr-x   2 arcc-t05 arcc-t05  4096 Aug 10 17:00 Documents

Answers(2)

2: How can you find out what the –al options do?

Use man ls or ls --help
-a, --all do not ignore entries starting with .
-l use a long listing format

Options are also case sensitive:

[arcc-t05@blog1 ~]$ ls -A
.bash_history  .bash_profile  .config  Documents  .emacs     .kshrc    .mozilla  .zshrc
.bash_logout   .bashrc        Desktop  Downloads  .esd_auth  .lesshst  .sshWhat does the pwd command do?

Answers(3, 4)

3: What does the pwd command do?

Use man pwd or pwd --help
pwd - print name of current/working directory

4: From the command line, what happens if you press the up/down arrow keys?

Steps through the previous commands you’ve typed.

Getting Started with Linux

The Linux File System

Using the Terminal

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