Searching in linux

Searching in linux

In Linux there are two commands for searching through files and directories.

1)       Grep.

2)      Find.

The grep command searches the contents of files and can extract information from them according to the pattern specified by us. The find command locates files and directories according to our query.

GREP -

By the help of grep command you can search through files to print lines containing specified words and phrases. And here we need not to bother to open the file with an editor.

Syntax - grep options expression filename

Examples of options in Grep

-v

Reverses the normal use of the grep command - Instead of selecting lines, it rejects the lines that match the given criteria.

-c

It only prints the total line count of matching lines.

-i

Ignores the case of the text when matching the given pattern.

-w

Checks if the given pattern is a word by itself and not a part of another word.

-l

Only gives the names of the files in which the given pattern was found

Expression is the word or phrase you want to find.

Filename is the name of the file or files you want to search.

For example, if you wanted to find all lines containing the word "hill" in a file named "MLK" use -

grep hill MLK

Output –

unity% grep hill MLK

I have a dream that one day on the red hills of Georgia, sons of...

hill and mountain shall be made low, the rough places shall be made...

So let freedom ring from the prodigious hilltops of New...

Let freedom ring from every hill and molehill of Mississippi,...

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To search through a directory of files for every occurence of a word or phrase, use the syntax grep word *

For instance, using the command grep people * might produce a list like the following:

unity% grep people *

my_speech:people who are self-employed.

my_speech:too few people in too many rooms. I recommend three

my_speech:paper is about how several people

old_speech:people working on a project together, but a broader

from_boss:say that co. should not be afraid of people

grep: Read error on work_dir: Is a directory

The name of each file containing the sought word is listed, along with the line in that file containing the word. The last line of this example is an error message generated when the grep command attempted to read a directory. In most cases (such as this one) these errors can be ignored.

Searching for files (find)

The find command searches for files according to their name.

Syntax - find pathname expression

The pathname is the directory where you want the search to begin; in most instances just put a period (.) to represent the current directory and all subdirectories.

You should use find to search only within your own directories. If you attempt to search someone else's, the search will take much longer and you will be denied access to many of the directories that the find command locates.

To search your home directory (and all directories within it) for a file named "elmrc" you would enter

find . -name elmrc -print

unity% find . -name elmrc -print

./.elm/elmrc

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In this example

. is the pathname, the directory from which find begins its search.

-name elmrc indicates what find should search for (a file named "elmrc").

-print instructs find to print the results of its search to the screen.

The find results indicate that the "elmrc" file is in the ".elm" directory which is in the current directory.

If you're not sure what file you're looking for, you can use wildcard characters, provided they're

enclosed in quotation marks.

For instance, to search for all files starting with the "elm" you would enter the command

 find . –name "elm*" -print

unity% find . -name "elm*" -print

./.elm/elmrc

./.elm/elmrc.old

./misc/elm.saving

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