Basic Linux Commands

  • grep [options] pattern [files]
    • -c : This prints only a count of the lines that match a pattern
    • -i : Ignores, case for matching
    • -w : Match whole word
    • grep -i "UNix" <file_Name>
    • grep -v "#" <file_Name>                                        -v option tells grep to invert its output
    • find . -name “*.txt” | grep –i JayZ | grep –vi “remix”
    • grep -n "ERROR" <file_Name>                             returns line # of search pattern
    • grep -wr "ERROR" *                                               -r recursively search for word in subdirectories
    • egrep -wr "one|new" *                                         filter with OR
  • File Handling
    • Touch command to create a file of 0kb size.     
      • touch <file_Name>
    • Vi command to edit a file using
      • vi <fileName>
      • ESC :q! Enter to exit without save
      • ESC :wq Enter  to exit & save
    • Cat command to view a file                               
      • cat <file_Name>
    • Less command                                                      
      • less <file_Name>          
      • Press Q to close the file
  • Editing File
    • Sed command
      • Substitution/replace in file
      • sed -i 's/linux/unix/'  <file_Name>           for single occurrence in each line
      • sed -i 's/linux/unix/g' <file_Name>          for all occurrences in all lines
      • sed -i '3 s/linux/unix/' <file_Name>         for 1st occurrence in 3rd lines
      • sed -i '3 s/linux/unix/g' <file_Name>       for all occurrence in 3rd lines
      • sed -i '1,3 s/linux/unix/g' <file_Name>    for all occurrence in 1st to 3rd line
      • sed -i '3,$ s/linux/unix/g' <file_Name>    for all occurrence in 3rd to last line
      • sed -i 's/linux/unix/p' <file_Name>          print replaced lines again
      • Deletion in file
      • sed -i 'nd' <file_Name>                            delete nth line
      • sed -i '$d' <file_Name>                            delete last line
      • sed -i 'x,yd' <file_Name>                         delete from range x to yth line
      • sed -i '/pattern/d' <file_Name>                delete pattern matching line e.g sed -i '/ERROR/d' <file_Name>     
      •                                                                   lines containing ERROR are deleted.             
    • awk:  Awk is abbreviated from the names of the developers – Aho, Weinberger, and Kernighan.
      • It is a scripting language used for manipulating data and generating reports.
      • The awk command programming language requires no compiling, 
      • and allows the user to use variables, numeric functions, string functions, and logical operators.
      • print content of file
        • awk '{print}' <file_Name>
      • print content of file which matches pattern "manager"
        • awk '/pattern/ {print}' <file_Name>       
      • print content of file only column 1 and 2 separated by space delimiter
        • awk '{print $1,$2}' <file_Name>              
      • print content of file only column 1 separated by - delimiter as defined in command
        • awk  -F"-"'  '{print $1}'  <file_Name>
      • print content of file with ROW NUMBER NR and all content with $0
        • awk '{print NR,$0}' <file_Name>             
      • print content of file with ROW NUMBER NR and only last column $NF
        • awk '{print NR,$NF}' <file_Name>             
      • print content of file with ROW NUMBER NR and all content with $0 from 3 to 6 row.
        • awk ' NR==3 , NR==6 {print NR,$0}' <file_Name>             
      • print all only if column 3 contains B6
        • awk '{ if($3 == "B6") print $0;}' <file_Name>      
      • for loop
        • awk 'BEGIN { for(i=1;i<=6;i++) print "square of", i, "is",i*i; }'                
  • Find command
    • Find all files in current directory and subdirectory
      • find -type f
    • Find all directories in current directory and subdirectory
      • find -type d
    • Find file using name and Ignore the case in home directory
      • find /home -iname newFile.txt
    • Find file using name in current directory
      • find . -name newFile.txt
    • Find directories using Name
      • find / -type d -name Documents
    • Find last 50 days modified file
      • find / -mtime +50
    • Find last 50 days accessed file
      • find / -atime +50
    • Find changed file in last 60 min
      • find / -cmin +60
    • Find accessed file in last 60 min
      • find / -amin +60
    • Find greater than 50MB file
      • find . -size +50M
    • Find less than 50MB file
      • find . -size -50M
    • Find 50MB file
      • find . -size 50M
    • Find the file with extension
      • find /root -name '*.txt'
      • find . -name '*.c' -print
      • find . -name \*.c -print
      • find . -perm -666
      • find . -perm /u=w,g=w
    • find directories having permission 777
      • find /root -type d -perm 777
    • find files having permission 655
      • find /root -type f -perm 777


  • Cut and paste:
    • Position the cursor where you want to begin cutting.
    • Press v to select characters (or uppercase V to select whole lines).
    • Move the cursor to the end of what you want to cut.
    • Press d to cut (or y to copy).
    • Move to where you would like to paste.
    • Press P to paste before the cursor, or p to paste after.
    • Copy and paste is performed with the same steps except for step 4 
    • where you would press y instead of d:
    • d = delete = cut   y = yank = copy
  • more to come

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