What is grep command and its different options?

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What is grep command and its different options?

Grep is a Linux / Unix command-line tool used to search for a string of characters in a specified file. The text search pattern is called a regular expression. When it finds a match, it prints the line with the result. The grep command is handy when searching through large log files.

What are the different grep commands available in Unix?

The grep command supports a number of options for additional controls on the matching:

  • -i: performs a case-insensitive search.
  • -n: displays the lines containing the pattern along with the line numbers.
  • -v: displays the lines not containing the specified pattern.
  • -c: displays the count of the matching patterns.

What is difference between grep and find command in Unix?

The main difference between grep and find command in UNIX is that the grep is a command that helps to search content and display them according to the user-specified regular expression while the find command helps to search and locate files according to the given criteria.

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Why is GNU grep so fast?

GNU grep is fast because it AVOIDS LOOKING AT EVERY INPUT BYTE. GNU grep is fast because it EXECUTES VERY FEW INSTRUCTIONS FOR EACH BYTE that it does look at.

What are the differences between Su and Su -?

su – logs you in completely as root, whereas su makes it so you are pretending to be root. The most obvious example of this is that ~ is root’s home directory if you use su – , but your own home directory if you use su .

Why do we use grep command in Unix?

The grep filter searches a file for a particular pattern of characters, and displays all lines that contain that pattern. The pattern that is searched in the file is referred to as the regular expression (grep stands for globally search for regular expression and print out).

What is difference between grep and egrep?

The main difference between grep and egrep is that grep is a command that allows searching content according to the given regular expression and displaying the matching lines while egrep is a variant of grep that helps to search content by applying extended regular expressions to display the machining lines.

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What is the difference between awk and grep?

Grep and awk can be used at the same time to narrow down the search enhance results. Grep is a simple tool to use to quickly search for matching patterns but awk is more of a programming language which processes a file and produces an output depending on the input values.

What is the difference between awk and sed?

The main difference between sed and awk is that sed is a command utility that works with streams of characters for searching, filtering and text processing while awk more powerful and robust than sed with sophisticated programming constructs such as if/else, while, do/while etc.

What does the su command do?

The Unix command su, which stands for ‘substitute user’ (originally ‘superuser’ ), is used by a computer user to execute commands with the privileges of another user account. When executed it invokes a shell without changing the current working directory or the user environment.

What is the difference between egrep and -E in Linux?

The egrep command is shortcut for grep binary, but with one exception, when grep is invoked as egrep the grep binary activates its internal logic as it would be called as grep -E. The difference is that -E option enables usage of extended regexp patterns.

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What are the different types of regular expressions in GNU grep?

grep understands three different versions of regular expression syntax: “basic,” “extended” and “perl.” In GNU grep, there is no difference in available functionality between basic and extended syntaxes. In other implementations, basic regular expressions are less powerful.

What is the difference between Grep and sed command?

However, if we stretch beyond this simple exercise, we’ll find that grep is only good for simple text matching and printing. On the other hand, in addition to match and print text, sed offers additional text transformation commands like substitution.

What is GNU grep -E used for?

GNU grep -E attempts to support traditional usage by assuming that { is not special if it would be the start of an invalid interval specification. For example, the command grep -E ‘ {1’ searches for the two-character string {1 instead of reporting a syntax error in the regular expression.