egrep

Linux Command – egrep ใช้ในการค้นหาบรรทัดใน file ที่ตรงเงื่อนไข

คำสั่ง

จากตัวอย่าง file test1

$ cat test1
Ant
Bee
Cat
Dog
Fly

1. ค้นหาบรรทัดที่มี text ตรงเงือนไข

egrep <text> <file>

$ egrep a test1
Cat
Man

$ egrep an test1
Man

2. ค้นหาบรรทัดที่มี text ใน list เงื่อนไข (|)

egrep “<text|text>” <file>

$ egrep "a|o" test1
Cat
Dog
Man

3. ค้นหาบรรทัดที่มี text ตรงเงื่อนไข โดยไม่สนใจตัวเล็กตัวใหญ่

egrep -i <text> <file>

$ egrep -i "a|o" test1
Ant
Cat
Dog
Man

4. ค้นหาบรรทัดที่ไม่มี text ตามเงื่อนไข

egrep -v <text> <file>

$ egrep -vi "a|o" test1
Bee
Fly

โครงสร้างคำสั่ง

 egrep [OPTIONS] PATTERN [FILE...]
 egrep [OPTIONS] [-e PATTERN]... [-f FILE]... [FILE...]

รายละเอียด

เป็นคำสั่งที่ใช้ค้นหาบรรทัดใน file ที่ตรงเงื่อนไข มีความสามารถที่สูงกว่า grep ตรงสามารถหาได้ค้นหาด้วยเงือนไขมากกว่า 1 คำ

Option

 --help Output a usage message and exit.

 -V, --version
 Output the version number of grep and exit.

 Matcher Selection
 -E, --extended-regexp
 Interpret PATTERN as an extended regular expression (ERE, see below).

 -F, --fixed-strings
 Interpret PATTERN as a list of fixed strings (instead of regular expressions), separated by newlines, any of which is to be matched.

 -G, --basic-regexp
 Interpret PATTERN as a basic regular expression (BRE, see below). This is the default.

 -P, --perl-regexp
 Interpret the pattern as a Perl-compatible regular expression (PCRE). This is highly experimental and grep -P may warn of unimplemented features.

 Matching Control
 -e PATTERN, --regexp=PATTERN
 Use PATTERN as the pattern. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to
 protect a pattern beginning with “-”.

 -f FILE, --file=FILE
 Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file
 contains zero patterns, and therefore matches nothing.

 -i, --ignore-case
 Ignore case distinctions in both the PATTERN and the input files.

 -v, --invert-match
 Invert the sense of matching, to select non-matching lines.

 -w, --word-regexp
 Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-
 word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters,
 digits, and the underscore.

 -x, --line-regexp
 Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $.

 -y Obsolete synonym for -i.

 General Output Control
 -c, --count
 Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see below), count non-matching lines.

 --color[=WHEN], --colour[=WHEN]
 Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers, byte offsets, and separators (for fields and groups of context lines) with
 escape sequences to display them in color on the terminal. The colors are defined by the environment variable GREP_COLORS. The deprecated environment variable GREP_COLOR
 is still supported, but its setting does not have priority. WHEN is never, always, or auto.

 -L, --files-without-match
 Suppress normal output; instead print the name of each input file from which no output would normally have been printed. The scanning will stop on the first match.

 -l, --files-with-matches
 Suppress normal output; instead print the name of each input file from which output would normally have been printed. The scanning will stop on the first match.

 -m NUM, --max-count=NUM
 Stop reading a file after NUM matching lines. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is
 positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search.
 When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM.
 When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines.

 -o, --only-matching
 Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line.

 -q, --quiet, --silent
 Quiet; do not write anything to standard output. Exit immediately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages
 option.

 -s, --no-messages
 Suppress error messages about nonexistent or unreadable files.

 Output Line Prefix Control
 -b, --byte-offset
 Print the 0-based byte offset within the input file before each line of output. If -o (--only-matching) is specified, print the offset of the matching part itself.

 -H, --with-filename
 Print the file name for each match. This is the default when there is more than one file to search.

 -h, --no-filename
 Suppress the prefixing of file names on output. This is the default when there is only one file (or only standard input) to search.

 --label=LABEL
 Display input actually coming from standard input as input coming from file LABEL. This is especially useful when implementing tools like zgrep, e.g., gzip -cd foo.gz |
 grep --label=foo -H something. See also the -H option.

 -n, --line-number
 Prefix each line of output with the 1-based line number within its input file.

 -T, --initial-tab
 Make sure that the first character of actual line content lies on a tab stop, so that the alignment of tabs looks normal. This is useful with options that prefix their
 output to the actual content: -H,-n, and -b. In order to improve the probability that lines from a single file will all start at the same column, this also causes the line
 number and byte offset (if present) to be printed in a minimum size field width.

 -u, --unix-byte-offsets
 Report Unix-style byte offsets. This switch causes grep to report byte offsets as if the file were a Unix-style text file, i.e., with CR characters stripped off. This will
 produce results identical to running grep on a Unix machine. This option has no effect unless -b option is also used; it has no effect on platforms other than MS-DOS and
 MS-Windows.

 -Z, --null
 Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -lZ outputs a zero byte after each file name
 instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be
 used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters.

 Context Line Control
 -A NUM, --after-context=NUM
 Print NUM lines of trailing context after matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or
 --only-matching option, this has no effect and a warning is given.

 -B NUM, --before-context=NUM
 Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or
 --only-matching option, this has no effect and a warning is given.

 -C NUM, -NUM, --context=NUM
 Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching option, this has no
 effect and a warning is given.

 File and Directory Selection
 -a, --text
 Process a binary file as if it were text; this is equivalent to the --binary-files=text option.

 --binary-files=TYPE
 If the first few bytes of a file indicate that the file contains binary data, assume that the file is of type TYPE. By default, TYPE is binary, and grep normally outputs
 either a one-line message saying that a binary file matches, or no message if there is no match. If TYPE is without-match, grep assumes that a binary file does not match;
 this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. When processing binary data,
 grep may treat non-text bytes as line terminators; for example, the pattern '.' (period) might not match a null byte, as the null byte might be treated as a line terminator.
 Warning: grep --binary-files=text might output binary garbage, which can have nasty side effects if the output is a terminal and if the terminal driver interprets some of it
 as commands.

 -D ACTION, --devices=ACTION
 If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files.
 If ACTION is skip, devices are silently skipped.

 -d ACTION, --directories=ACTION
 If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip,
 silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is
 equivalent to the -r option.

 --exclude=GLOB
 Skip files whose base name matches GLOB (using wildcard matching). A file-name glob can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character
 literally.

 --exclude-from=FILE
 Skip files whose base name matches any of the file-name globs read from FILE (using wildcard matching as described under --exclude).

 --exclude-dir=DIR
 Exclude directories matching the pattern DIR from recursive searches.

 -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option.

 --include=GLOB
 Search only files whose base name matches GLOB (using wildcard matching as described under --exclude).

 -r, --recursive
 Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the
 working directory. This is equivalent to the -d recurse option.

 -R, --dereference-recursive
 Read all files under each directory, recursively. Follow all symbolic links, unlike -r.

 Other Options
 --line-buffered
 Use line buffering on output. This can cause a performance penalty.

 -U, --binary
 Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses the file type by looking at the contents of the first 32KB read from the file. If grep
 decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U
 overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line,
 this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows.

 -z, --null-data
 Treat the input as a set of lines, each terminated by a zero byte (the ASCII NUL character) instead of a newline. Like the -Z or --null option, this option can be used with
 commands like sort -z to process arbitrary file names.

กลุ่มคำสั่ง

awk(1), cmp(1), diff(1), find(1), gzip(1), perl(1), sed(1), sort(1), xargs(1), zgrep(1), read(2), pcre(3), pcresyntax(3), pcrepattern(3), terminfo(5), glob(7), regex(7)

Reference:

คำสั่ง Unix – Linux Command

Linux, Unix

Author: Suphakit Annoppornchai

Credit: https://saixiii.com