How to find number of cpu cores and cpu info

nproc

the nproc command will output the number of cpu cores you have.

eg:
$ nproc
2

lscpu

cpu info are stored in the file /proc/cpuinfo .lscpu command will list the details in the file in a human readable format.


eg:
$ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                2
On-line CPU(s) list:   0,1
Thread(s) per core:    1
Core(s) per socket:    2
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 23
Stepping:              10
CPU MHz:               1200.000
BogoMIPS:              5422.43
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              2048K
NUMA node0 CPU(s):     0,1

cat /proc/cpuinfo

you can directly view  the content of /proc/cpuinfo using the cat command

eg:
$ cat /proc/cpuinfo
processor    : 0
vendor_id    : GenuineIntel
cpu family    : 6
model        : 23
model name    : Pentium(R) Dual-Core  CPU      E5400  @ 2.70GHz
stepping    : 10
microcode    : 0xa0b
cpu MHz        : 1200.000
cache size    : 2048 KB
physical id    : 0
siblings    : 2
core id        : 0
cpu cores    : 2
apicid        : 0
initial apicid    : 0
fpu        : yes
fpu_exception    : yes
cpuid level    : 13
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm xsave lahf_lm dtherm tpr_shadow vnmi flexpriority
bogomips    : 5422.43
clflush size    : 64
cache_alignment    : 64
address sizes    : 36 bits physical, 48 bits virtual
power management:

processor    : 1
vendor_id    : GenuineIntel
cpu family    : 6
model        : 23
model name    : Pentium(R) Dual-Core  CPU      E5400  @ 2.70GHz
stepping    : 10
microcode    : 0xa0b
cpu MHz        : 1200.000
cache size    : 2048 KB
physical id    : 0
siblings    : 2
core id        : 1
cpu cores    : 2
apicid        : 1
initial apicid    : 1
fpu        : yes
fpu_exception    : yes
cpuid level    : 13
wp        : yes
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm xsave lahf_lm dtherm tpr_shadow vnmi flexpriority
bogomips    : 5422.43
clflush size    : 64
cache_alignment    : 64
address sizes    : 36 bits physical, 48 bits virtual
power management:

Searching inside files with grep

• The “grep” command can be used to search inside files.

                                $ grep word filename

        

         Ex: to find the lines having the word "File" inside a file named foo.txt

• if you need to match the whole word use the -w option with grep

                             $ grep -w 'word' filename

       Ex: in the previous example even though you searched for the word "File" other words which contain the word "File" as a part of it also got selected.by using -w option we can avoid that

      Ex: i have a file named yumlist.txt containing names of packages,and there are thousands of package names in that file.i need to find the package gcj from that file.if i just search using grep other packages which has gcj as a part of its name will also get selected(eg:-libgcj) , but when i use grep with -w option only the gcj packages will get selected

    

• to ignore case use -i option

         Ex:the word "File" in the file foo.txt starts with a capital "F" ,if i just  search as "file" no line will get selected, but when -i option is used, grep will ignore the case and select the lines.
 

          

• to recursively search files in current directory and all its sub directories use the “grep” command with -r option

   Ex : i need to find if there are any servlet source code files present in the current directory or any of its sub directories.

• to display the line numbers of the lines containing the matching word use -n option

• to list only the file names of the files containing the matching word use the -l option with grep

• grep can also be used to search inside outputs generated by other commands using a pipe

                           $ command | grep 'word'

   

                 Ex : I'm in the directory /usr/bin and i need to find all the icewm files in that directory.

                        if i just type ls 3626 files will be displayed

               so i direct the output of ls command to a grep command and search for icewm files

• you can also use regular expressions when searching using the “grep” command

            

                                    $ grep “regular expression” filename

                                                                  or

                                   $ grep -e “regular expression” filename

                                                           or

                                  $ grep --regexp=“regular expression” filename

Ex: website1.sql is a backup file of an sql database having data on customers,items,orders,purchases,etc . i need to find the customer email addresses ending with a .com from that file.

if you want to learn more on using regular expressions using grep click here

cat and more

“cat” command

 

the cat command can be used to display contents of files ,write into files or to concatenate files.

Displaying a file using “cat” command

     

        $ cat filename

   ex:

  

Writing into files using “cat” command

        $ cat > filename

            #things to be

            # written

            #in the file

            #

once you finish press enter to go to a new line and then press ctrl +D to close file.

   ex:

 

Appending in to a file using “cat” command

      similar to writing a file using cat but use >>

           $ cat >> filename

             # new content

            #to be appended

            #to the file

   ex:

Concatenating files using “cat” command

several files can be concatenated to a single file using cat command

           $ cat file1 file2 file3 > newFile

(* this is useful to merge a file that has been split into several parts by the “split” command )

   ex:

“more” command

The “cat” command displays the entire file at once. So it maybe a disadvantage when viewing a large file using cat because we may only see the last part of the file. Therefore viewing large files the “more” command is a better option.

The “more” command displays a file page by page. 

           $ more filename

Basic File Handling ( Copy ,Move,Rename ,Delete )

"cp" command

     used to copy files.

          cp filepath/filename  destination/filename

        or

         cp filepath/filename  destination

   ex:
        $ cp exit.png  mydir/q.png

               copies the file exit.png into mydir as q.png

        $ cp Library.sql  mydir

            copies the file Library.sql inside the directory mydir

  copying multiple files ex:

"mv" command

     used to move files

       ex:
          $ mv out1-1.ogv mydir/out1-1.ogv

          the file out1-1.ogv is moved in to mydir

    moving multiple files with mv

         mv file1 file2 file3 destination 

 ex:

   use * when copying or moving files to copy or move all the files in the   current directory     

   the "mv" command can be also used to rename files

   ex :

"rename" command

         used to rename files

        rename a b c

      a  - part of the file name to be renamed
      b - new part of the filename
      c - the file

   ex: to rename a file named "aa" to "newAA"

      $ rename  aa  newAA  aa

      to rename the "newAA" as "oldAA" only the part "new" has to be renamed to old

      $ rename new old newAA

 using " -v " option with the command rename prints what is going to be done

 ex: to change the extension of all the png files to jpg

    $ rename -v png jpg *.png

"rm" command

      used to delete files

      rm filepath/filename

     ex:  $ rm myfile
 
         deletes the file named myfile in current directory    

    deleting multiple files with rm

   ex:   $ rm file1 file2 file3

Creating and Deleting Directories

"mkdir"  command

          used to create directories. 
  
eg: creating a directory using mkdir

  $ mkdir mydir1
  $ ls
   exit.png  Library.sql  mydir1  out1-1.ogv 

     creating multiple directories using mkdir

$ mkdir mydir2 mydir3
$ ls
exit.png  Library.sql  mydir1  mydir2  mydir3  out1-1.ogv  

"rmdir" command 

      used to delete directories

  eg: deleting a single directory

       $rm mydir1
       $ls
       exit.png  Library.sql mydir2 mydir3 out1-1.ogv 

      deleting multiple directories

       $ rmdir mydir2 mydir3
       $ ls
       exit.png  Library.sql  mydir1  out1-1.ogv 


     but you will get an error saying  rmdir: failed to remove `directory name': Directory not empty if you try to delete a directory containing files.

To forcefully delete directories containing files we have to use "rm" command with command line argument -rf

 ex:
     $ rmdir -rf mydir1

Basic Terminal Navigation Commands

"cd"  command 

             used to change the current directory
         
       cd directoryName   or  cd fullpath/directoryName

 ex:
   [ravindu@localhost ~]$ cd Desktop
   [ravindu@localhost Desktop]$

   [ravindu@localhost Desktop]$ cd /home/ravindu/Documents
   [ravindu@localhost Documents]$

   to go back to the previous directory use cd ..

  ex:
     [ravindu@localhost Documents]$ cd ..
     [ravindu@localhost ~]$

 

"ls" command

   used to list files and directories of the current directory
   ex:

ls -a
   displays all the files in the current directory including hidden files
   ex:

ls -l
   displays long list of files in the current directory with  details

   ex:

to view all other available command line arguments for ls command type
ls --help


"pwd" command
       prints the current directory

 ex:
     [ravindu@localhost Documents]$ pwd
     /home/ravindu/Documents