Bash Index : S - The 'S' Bash commands : description, flags and examples

1. check subscription status (not subscribed so far) :
   subscription-manager status

   +-------------------------------------------+
       System Status Details
   +-------------------------------------------+
   Overall Status: Unknown

2. subscription-manager config --server.proxy_hostname=10.27.26.37 --server.proxy_port=3128
3. Depending on context :
   • subscription-manager register --username kevin --password 'P@ssw0rd' --auto-attach
   • subscription-manager register --username kevin --password 'P@ssw0rd' --org=1234567

   	Registering to: subscription.rhsm.redhat.com:443/subscription
   	The system has been registered with ID: aaaaaaa8-bbb4-ccc4-ddd4-eeeeeeeeee12
   	The registered system name is: myNewRedHatMachine

4. check :
   subscription-manager status

   +-------------------------------------------+
      System Status Details
   +-------------------------------------------+
   Overall Status: Current
   
   System Purpose Status: Not Specified		not relevant
   
   

   subscription-manager list

   +-------------------------------------------+
       Installed Product Status
   +-------------------------------------------+
   Product Name:   Red Hat Enterprise Linux for x86_64
   Product ID:     479
   Version:        9.1
   Arch:           x86_64
   Status:         Subscribed
   Status Details:
   Starts:         01/01/2023
   Ends:           01/01/2024

Successfully attached a subscription for: Red Hat Enterprise Linux for Virtual Datacenters, Standard

Detailed procedure :

● smbd.service - Samba SMB Daemon
	Loaded: loaded (/lib/systemd/system/smbd.service; enabled; vendor preset: enabled)
	Active: active (running) since Thu 2018-11-29 08:36:29 CET; 1 weeks 0 days ago
	

dev-mapper-hostname\x2d\x2dvg\x2dswap_1.swap: Unit is bound to inactive unit dev-mapper-hostname\x2d\x2dvg\x2dswap_1.device. Stopping, too.
var.mount: Unit is bound to inactive unit dev-mapper-hostname\x2d\x2dvg\x2dvar.device. Stopping, too.
tmp.mount: Unit is bound to inactive unit dev-mapper-hostname\x2d\x2dvg\x2dtmp.device. Stopping, too.

halt

display a stop screen like System halted. At that step, it is safe to press the physical Power off button.

power-off

send an ACPI command to signal the PSU to disconnect main power.

• L : the corresponding stream will be line buffered. This option is invalid with standard input.
• 0 : the corresponding stream will be unbuffered

tail -f access.log | stdbuf -oL cut -d ' ' -f1 | uniq

journalctl -u ssh | cut -d ' ' -f6- | uniq
journalctl -u ssh | stdbuf -oL cut -d ' ' -f6- | uniq

	==> both _seem_ to behave the same. Maybe "journalctl" is not a good candidate to experiment on this ;-)

1. script /path/to/typescript/file
2. the commands you type and their output is recorded into /path/to/typescript/file but not recorded in real time, unless -f is used
3. stop recording :
   • exit
   • CTRL-d
4. You can now view the typescript :
   • cat /path/to/typescript/file
   • less -R /path/to/typescript/file

State filters :

Address filters :

root
Tue Feb 27 02:53:52 PM CET 2024
Hello World

strerror
%s: I/O error
error setting limit (%s)
Syntax error: %s

  File: myFile
  Size: 26583103        Blocks: 51928      IO Block: 4096   regular file
Device: 811h/2065d      Inode: 13          Links: 1
Access: (0600/-rw-------)  Uid: ( 1000/   bob)   Gid: ( 1000/   bob)
Access: 2024-09-24 16:28:57.600939443 +0200
Modify: 2024-07-24 06:41:34.000000000 +0200
Change: 2024-09-22 18:42:31.159554215 +0200
 Birth: 2024-08-16 10:39:18.755412316 +0200

-rw------- 1 bob users 3413 Dec  9 12:05 chunk_00
-rw------- 1 bob users 3413 Dec  9 12:05 chunk_01
-rw------- 1 bob users 3414 Dec  9 12:05 chunk_02
9e5dfea5493c78eaee1e1e7158d063ad  ./tmp.4iNzQxgGae			checksums match 
9e5dfea5493c78eaee1e1e7158d063ad  ./tmp.4iNzQxgGae_REASSEMBLED	meaning we've successfully re-assembled the chunks into an exact copy of the original file

• someFile is executed even though its execution bit is not set
• someFile is executed within the current shell context, which allows :
  • loading variables into the current interactive shell session :
    1. source myConfigFile
    2. other commands using variables
  • using someFile as a configuration file for a script, without leaving variables in the shell environment once the script is over :
    sourcedFile=$(mktemp sourcedFile.XXXXXXXX); echo 'value=42' > "$sourcedFile"; chmod -x "$sourcedFile"; scriptFile=$(mktemp scriptFile.XXXXXXXX); echo "source $sourcedFile; echo 'sourced'; echo \"during the script : \\\$value='\$value'\"" > "$scriptFile"; chmod +x "$scriptFile"; ls -l "$sourcedFile" "$scriptFile"; cat "$sourcedFile" "$scriptFile"; ./"$scriptFile"; echo "after the script : \$value='$value'"; rm "$sourcedFile" "$scriptFile"

    value=42	cat "$sourcedFile"
    source sourcedFile.akr6paIl; echo 'sourced'; echo "during the script : \$value='$value'"	cat "$scriptFile"
    sourced		started running the script
    during the script : $value='42'	the variable exists in the script context
    after the script : $value=''	no value anymore

    Since a dedicated subshell (having its own context) is spawned when executing a script, if you want variables to survive for future scripts or commands after the script ends, you'll have to :

    • export variables within the script (details)
    • or source the script
• The return status is the exit status of the last command executed from someFile, or zero if no commands are executed.

Trying to source a file having DOS line endings led the shell to complain for syntax errors on EVERY line. Consider converting line endings into DOS format.

configFile='./script.conf'; scriptFile='./script.sh'; echo -e '#!/usr/bin/env bash\nvar1=value1\nexport var2=value2' > "$configFile"; echo -e '#!/usr/bin/env bash\necho "\tvar1 = $var1"\necho "\tvar2 = $var2"' > "$scriptFile"; echo -e "\n'source'd config file :"; cat "$configFile"; source "$configFile"; echo -e "\nCommand line (current shell context) :\n\tvar1 = $var1\n\tvar2 = $var2\n\nScript (subshell context) :"; bash "./$scriptFile"; rm "$configFile" "$scriptFile"

'source'd config file :
#!/usr/bin/env bash
var1=value1			not exported
export var2=value2

Command line (current shell context) :
	var1 = value1		exists 
	var2 = value2

Script (subshell context) :
	var1 =			unset 
	var2 = value2

• script.conf :

  variable='value'

• script.sh :

  #!/usr/bin/env bash
  
  source script.conf
  
  ... do something with "$variable" ...

Then no shebang is required in the configuration file script.conf. It may also be a safe practice to remove its execution permissions.

grep ' 500 ' 2012-07-03-apache-access.log | cut -d ' ' -f 11 | sort | uniq -c | sort -nr | less

All the magic is in the uniq -c prior to sorting.

• echo '2 20 3 1' | tr ' ' '\n' | sort -n | tr '\n' ' '

  1 2 3 20

• echo 'banana,coconut,apple' | tr ',' '\n' | sort | tr '\n' ','

  apple,banana,coconut,

• Whether data is sorted numerically, alphabetically, ascending, descending, is just a matter of adding the appropriate ordering option(s).
• to sort version numbers, consider sort -V

sort numbers ascending

cat << EOF | sort
51
63
42
EOF

42
51
63

sort by a specific digit :

cat << EOF | sort -k1.2
51
63
42
EOF

51
42
63

cat << EOF | sort -k1.2r
51
63
42
EOF

63
42
51

sort by the 2^nd then 3^rd digit, ascending

cat << EOF | sort -k1.2,1.3
8120
7268
9147
EOF

8120
9147
7268

sort by column 2, then by column 1

3 0
1 1		sorting on column 1 only makes sense
6 1		when items of column 2 are equal
2 4
1 7

• [ + ] : service is running
• [ - ] : service is stopped
• [ ? ] : unknown / doesn't reply to the "service status" command