Here’s a good tool I found for creating the date. A visual helper..
Archives
All posts for the day August 4th, 2012
history | awk ‘{print $2}’| awk ‘BEGIN {FS=”|”} {print $1}’| sort| uniq -c | sort -r
You may need to modify the first print $2 point to your column that has all your commands if you run a non-default history like I do.
$ sudo mkdir -p project/{lib/ext,bin,src,doc/{html,info,pdf},demo/stat/a}
Will create this
-- project— stat
|-- bin
|-- demo
|
| -- a— pdf
|-- doc
| |-- html
| |-- info
|
|– lib
| -- ext— src
Sed Command in Unix and Linux Examples
Sed is a Stream Editor used for modifying the files in unix (or linux). Whenever you want to make changes to the file automatically, sed comes in handy to do this. Most people never learn its power; they just simply use sed to replace text. You can do many things apart from replacing text with sed. Here I will describe the features of sed with examples.
Consider the below text file as an input.
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>cat file.txt unix is great os. unix is opensource. unix is free os. learn operating system. unixlinux which one you choose. |
Sed Command Examples
1. Replacing or substituting string
Sed command is mostly used to replace the text in a file. The below simple sed command replaces the word “unix” with “linux” in the file.
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>sed 's/unix/linux/' file.txt linux is great os. unix is opensource. unix is free os. learn operating system. linuxlinux which one you choose. |
Here the “s” specifies the substitution operation. The “/” are delimiters. The “unix” is the search pattern and the “linux” is the replacement string.
By default, the sed command replaces the first occurrence of the pattern in each line and it won’t replace the second, third…occurrence in the line.
2. Replacing the nth occurrence of a pattern in a line.
Use the /1, /2 etc flags to replace the first, second occurrence of a pattern in a line. The below command replaces the second occurrence of the word “unix” with “linux” in a line.
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>sed 's/unix/linux/2' file.txt unix is great os. linux is opensource. unix is free os. learn operating system. unixlinux which one you choose. |
3. Replacing all the occurrence of the pattern in a line.
The substitute flag /g (global replacement) specifies the sed command to replace all the occurrences of the string in the line.
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>sed 's/unix/linux/g' file.txt linux is great os. linux is opensource. linux is free os. learn operating system. linuxlinux which one you choose. |
4. Replacing from nth occurrence to all occurrences in a line.
Use the combination of /1, /2 etc and /g to replace all the patterns from the nth occurrence of a pattern in a line. The following sed command replaces the third, fourth, fifth… “unix” word with “linux” word in a line.
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>sed 's/unix/linux/3g' file.txt unix is great os. unix is opensource. linux is free os. learn operating system. unixlinux which one you choose. |
5. Changing the slash (/) delimiter
You can use any delimiter other than the slash. As an example if you want to change the web url to another url as
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>sed 's/http:\/\//www/' file.txt |
In this case the url consists the delimiter character which we used. In that case you have to escape the slash with backslash character, otherwise the substitution won’t work.
Using too many backslashes makes the sed command look awkward. In this case we can change the delimiter to another character as shown in the below example.
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>sed 's_http://_www_' file.txt >sed 's|http://|www|' file.txt |
6. Using & as the matched string
There might be cases where you want to search for the pattern and replace that pattern by adding some extra characters to it. In such cases & comes in handy. The & represents the matched string.
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>sed 's/unix/{&}/' file.txt {unix} is great os. unix is opensource. unix is free os. learn operating system. {unix}linux which one you choose. >sed 's/unix/{&&}/' file.txt {unixunix} is great os. unix is opensource. unix is free os. learn operating system. {unixunix}linux which one you choose. |
7. Using \1,\2 and so on to \9
The first pair of parenthesis specified in the pattern represents the \1, the second represents the \2 and so on. The \1,\2 can be used in the replacement string to make changes to the source string. As an example, if you want to replace the word “unix” in a line with twice as the word like “unixunix” use the sed command as below.
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>sed 's/\(unix\)/\1\1/' file.txt unixunix is great os. unix is opensource. unix is free os. learn operating system. unixunixlinux which one you choose. |
The parenthesis needs to be escaped with the backslash character. Another example is if you want to switch the words “unixlinux” as “linuxunix”, the sed command is
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>sed 's/\(unix\)\(linux\)/\2\1/' file.txt unix is great os. unix is opensource. unix is free os. learn operating system. linuxunix which one you choose. |
Another example is switching the first three characters in a line
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>sed 's/^\(.\)\(.\)\(.\)/\3\2\1/' file.txt inux is great os. unix is opensource. unix is free os. aelrn operating system. inuxlinux which one you choose. |
8. Duplicating the replaced line with /p flag
The /p print flag prints the replaced line twice on the terminal. If a line does not have the search pattern and is not replaced, then the /p prints that line only once.
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>sed 's/unix/linux/p' file.txt linux is great os. unix is opensource. unix is free os. linux is great os. unix is opensource. unix is free os. learn operating system. linuxlinux which one you choose. linuxlinux which one you choose. |
9. Printing only the replaced lines
Use the -n option along with the /p print flag to display only the replaced lines. Here the -n option suppresses the duplicate rows generated by the /p flag and prints the replaced lines only one time.
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>sed -n 's/unix/linux/p' file.txt linux is great os. unix is opensource. unix is free os. linuxlinux which one you choose. |
If you use -n alone without /p, then the sed does not print anything.
10. Running multiple sed commands.
You can run multiple sed commands by piping the output of one sed command as input to another sed command.
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>sed 's/unix/linux/' file.txt| sed 's/os/system/' linux is great system. unix is opensource. unix is free os. learn operating system. linuxlinux which one you chosysteme. |
Sed provides -e option to run multiple sed commands in a single sed command. The above output can be achieved in a single sed command as shown below.
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>sed -e 's/unix/linux/' -e 's/os/system/' file.txt linux is great system. unix is opensource. unix is free os. learn operating system. linuxlinux which one you chosysteme. |
11. Replacing string on a specific line number.
You can restrict the sed command to replace the string on a specific line number. An example is
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>sed '3 s/unix/linux/' file.txt unix is great os. unix is opensource. unix is free os. learn operating system. linuxlinux which one you choose. |
The above sed command replaces the string only on the third line.
12. Replacing string on a range of lines.
You can specify a range of line numbers to the sed command for replacing a string.
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>sed '1,3 s/unix/linux/' file.txt linux is great os. unix is opensource. unix is free os. learn operating system. linuxlinux which one you choose. |
Here the sed command replaces the lines with range from 1 to 3. Another example is
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>sed '2,$ s/unix/linux/' file.txt linux is great os. unix is opensource. unix is free os. learn operating system. linuxlinux which one you choose. |
Here $ indicates the last line in the file. So the sed command replaces the text from second line to last line in the file.
13. Replace on a lines which matches a pattern.
You can specify a pattern to the sed command to match in a line. If the pattern match occurs, then only the sed command looks for the string to be replaced and if it finds, then the sed command replaces the string.
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>sed '/linux/ s/unix/centos/' file.txt unix is great os. unix is opensource. unix is free os. learn operating system. centoslinux which one you choose. |
Here the sed command first looks for the lines which has the pattern “linux” and then replaces the word “unix” with “centos”.
14. Deleting lines.
You can delete the lines a file by specifying the line number or a range or numbers.
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>sed '2 d' file.txt >sed '5,$ d' file.txt |
15. Duplicating lines
You can make the sed command to print each line of a file two times.
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>sed 'p' file.txt |
16. Sed as grep command
You can make sed command to work as similar to grep command.
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>grep 'unix' file.txt >sed -n '/unix/ p' file.txt |
Here the sed command looks for the pattern “unix” in each line of a file and prints those lines that has the pattern.
You can also make the sed command to work as grep -v, just by using the reversing the sed with NOT (!).
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>grep -v 'unix' file.txt >sed -n '/unix/ !p' file.txt |
The ! here inverts the pattern match.
17. Add a line after a match.
The sed command can add a new line after a pattern match is found. The “a” command to sed tells it to add a new line after a match is found.
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>sed '/unix/ a "Add a new line"' file.txt unix is great os. unix is opensource. unix is free os. "Add a new line" learn operating system. unixlinux which one you choose. "Add a new line" |
18. Add a line before a match
The sed command can add a new line before a pattern match is found. The “i” command to sed tells it to add a new line before a match is found.
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>sed '/unix/ i "Add a new line"' file.txt "Add a new line" unix is great os. unix is opensource. unix is free os. learn operating system. "Add a new line" unixlinux which one you choose. |
19. Change a line
The sed command can be used to replace an entire line with a new line. The “c” command to sed tells it to change the line.
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>sed '/unix/ c "Change line"' file.txt "Change line" learn operating system. "Change line" |
20. Transform like tr command
The sed command can be used to convert the lower case letters to upper case letters by using the transform “y” option.
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>sed 'y/ul/UL/' file.txt Unix is great os. Unix is opensoUrce. Unix is free os. Learn operating system. UnixLinUx which one yoU choose. |
(pulled from http://www.folkstalk.com/2012/01/grep-command-in-unix-examples.html)
Grep Command in Unix and Linux Examples
Grep is the frequently used command in Unix (or Linux). Most of us use grep just for finding the words in a file. The power of grep comes with using its options and regular expressions. You can analyze large sets of log files with the help of grep command.
Grep stands for Global search for Regular Expressions and Print.
The basic syntax of grep command is
grep [options] pattern [list of files]
Let see some practical examples on grep command.
1. Running the last executed grep command
This saves a lot of time if you are executing the same command again and again.
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!grep |
This displays the last executed grep command and also prints the result set of the command on the terminal.
2. Search for a string in a file
This is the basic usage of grep command. It searches for the given string in the specified file.
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grep "Error" logfile.txt |
This searches for the string “Error” in the log file and prints all the lines that has the word “Error”.
3. Searching for a string in multiple files.
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grep "string" file1 file2 grep "string" file_pattern |
This is also the basic usage of the grep command. You can manually specify the list of files you want to search or you can specify a file pattern (use regular expressions) to search for.
4. Case insensitive search
The -i option enables to search for a string case insensitively in the give file. It matches the words like “UNIX”, “Unix”, “unix”.
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grep -i "UNix" file.txt |
5. Specifying the search string as a regular expression pattern.
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grep "^[0-9].*" file.txt |
This will search for the lines which starts with a number. Regular expressions is huge topic and I am not covering it here. This example is just for providing the usage of regular expressions.
6. Checking for the whole words in a file.
By default, grep matches the given string/pattern even if it found as a substring in a file. The -w option to grep makes it match only the whole words.
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grep -w "world" file.txt |
7. Displaying the lines before the match.
Some times, if you are searching for an error in a log file; it is always good to know the lines around the error lines to know the cause of the error.
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grep -B 2 "Error" file.txt |
This will prints the matched lines along with the two lines before the matched lines.
8. Displaying the lines after the match.
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grep -A 3 "Error" file.txt |
This will display the matched lines along with the three lines after the matched lines.
9. Displaying the lines around the match
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grep -C 5 "Error" file.txt |
This will display the matched lines and also five lines before and after the matched lines.
10. Searching for a sting in all files recursively
You can search for a string in all the files under the current directory and sub-directories with the help -r option.
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grep -r "string" * |
11. Inverting the pattern match
You can display the lines that are not matched with the specified search sting pattern using the -v option.
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grep -v "string" file.txt |
12. Displaying the non-empty lines
You can remove the blank lines using the grep command.
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grep -v "^$" file.txt |
13. Displaying the count of number of matches.
We can find the number of lines that matches the given string/pattern
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grep -c "sting" file.txt |
14. Display the file names that matches the pattern.
We can just display the files that contains the given string/pattern.
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grep -l "string" file.txt |
15. Display the file names that do not contain the pattern.
We can display the files which do not contain the matched string/pattern.
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grep -l "string" file.txt |
16. Displaying only the matched pattern.
By default, grep displays the entire line which has the matched string. We can make the grep to display only the matched string by using the -o option.
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grep -o "string" file.txt |
17. Displaying the line numbers.
We can make the grep command to display the position of the line which contains the matched string in a file using the -n option
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grep -n "string" file.txt |
18. Displaying the position of the matched string in the line
The -b option allows the grep command to display the character position of the matched string in a file.
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grep -o -b "string" file.txt |
19. Matching the lines that start with a string
The ^ regular expression pattern specifies the start of a line. This can be used in grep to match the lines which start with the given string or pattern.
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grep "^start" file.txt |
20. Matching the lines that end with a string
The $ regular expression pattern specifies the end of a line. This can be used in grep to match the lines which end with the given string or pattern.
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grep "end$" file.txt |
