Linux Commands Examples

A great documentation place for Linux commands

sed

stream editor for filtering and transforming text


see also : awk - ed - grep - tr

Synopsis

sed [OPTION]... {script-only-if-no-other-script} [input-file]...


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examples

1
line=$(echo "$line" |  sed 's/\//\\\//g');



will escape all slashes in the variable line
example added by LeBerger
1
sed -i 's/[ ]\+/ /g' 



will replace one or more space by one space, directly in the file.

In other word, it doesn't output the resulting string, but edit directly the file
example added by LeBerger
1
source

How to replace a list of strings by another list

This is basically your first idea, but with the substitution commands put into a file, so they’re more manageable:

tmpfile=/tmp/Asasuser.$$
exec 3< fileA
exec 4< fileB
while read –r astring <&3
do
        read –r bstring <&4
        echo "s/$astring/$bstring/" >> "$tmpfile"
done
exec 3<&- 4<&-
sed –f "$tmpfile" file1 > out
rm –f "$tmpfile"

This assumes that fileA and fileB have the same number of lines (and that that number is greater than zero) and that neither of them has any unescaped / characters.

0
line=$(echo "$line" |  sed 's/\//\\\//g');



will escape all slashes in the variable line
example added by LeBerger
0
sed -i 's/[ ]\+/ /g' 



will replace one or more space by one space, directly in the file.

In other word, it doesn't output the resulting string, but edit directly the file
example added by LeBerger
0
source
            
sed "s+^+$*+"
0
source
            
ifconfig | sed -f task_5.sed
0
source
            
sed -f $1.sed <OPS >$1.c
0
source
            
sed -n $1p
0
source
            
sed "s/ */ /g"
0
source
            
sed '1d' $@
0
source
            
sed -Ef ld_sed_pass_1 $1 | sed -f ld_sed_pass_2
0
source

sed: how to replace line if found or append to end of file if not found?

It's a bit easier in awk, although the "in place editing" is not automatic:

awk -v varname="FOOBAR" -v newval="newvalue" '
    BEGIN {FS = OFS = "="}
    $1 == varname {$2 = newval; found = 1}
    {print}
    END {if (! found) {print varname, newval}}
' file > tempfile &&
mv tempfile file

0
source

How to Remove the Last 2 Lines of a Very Large File

Try VIM...I'm not sure if it will do the trick or not, as I've never used it on such a big file, but I've used it on smaller larger files in the past give it try.

0
source

Edit first line of large text file

You can use less to see what you want to edit and use sed to make the changes. This way you edit without loading the entire file.

Another way is to split the file, edit and join again:

split -b 10000k <file>

and to join:

cat xa* > <file>

0
source

Search for files with more than one term (grep, awk?)

You can use either the -e or -f options to search for multiple expressions (from man grep):

    -e PATTERN, --regexp=PATTERN
          Use  PATTERN  as  the  pattern.   This  can  be  used to specify
          multiple search patterns, or to protect a pattern beginning with
          a hyphen (-).  (-e is specified by POSIX.)

   -f FILE, --file=FILE
          Obtain  patterns  from  FILE,  one  per  line.   The  empty file
          contains zero patterns, and therefore matches nothing.   (-f  is
          specified by POSIX.)

So you would use this as:

$ grep -e termA -e termB *

0
source

List only the device names of all available network interfaces

to just print the first column:

netstat -a | awk '{print $1}'

you can incorporate other rules in awk to add or remove entries as needed.

EDIT: same goes with ifconfig (like Doug pointed out)

ifconfig | awk '{print $1}'

This is an example excluding the 'lo' interface

ifconfig | awk '{if ($1 != lo) print $1}'

0
source

SQL like group by and sum for text files in command line?

You could a use a few lines of Lua to acheive this. Lua is available on a wide range of platforms including Windows and Linux.

-- Quick and dirty - no error checking, unsorted output

io.input('huge_text_file.txt')

results = {}

for line in io.lines() do
    for text, number in string.gmatch(line, '(%w+)%s+(%d+)') do
        results[text] = (results[text] or 0) + number
    end
end

for text, number in pairs(results) do
    print(text, number)
end

You can sort the output using any sort utility or a few more lines of Lua.

0
source

SED: How can I print every line after first instance of string using Sed?

Use a regular expression in the address:

sed -n '/^16:30/,$p'

or

sed '/^16:30/,$!d'

0
source

Prefix all lines with the first word in a file

Perl solution:

perl -pe 'print $prefix; ($prefix) = /^(.+? )/ if 1..1' INPUT.TXT

0
source

Using sed to Download ComboFix automatically

That's funny: I just went to http://www.bleepingcomputer.com/download/combofix/dl/12/ and found

<a href='http://download.bleepingcomputer.com/dl/587c6038..../..../ComboFix.exe'>click here</a>.

i.e., the URL is delimited by single quotes (') rather than double quotes (") (which is what your sed command is looking for).

description

Sed is a stream editor. A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline). While in some ways similar to an editor which permits scripted edits (such as ed), sed works by making only one pass over the input(s), and is consequently more efficient. But it is sed’s ability to filter text in a pipeline which particularly distinguishes it from other types of editors.

-n, --quiet, --silent

suppress automatic printing of pattern space

-e script, --expression=script

add the script to the commands to be executed

-f script-file, --file=script-file

add the contents of script-file to the commands to be executed

--follow-symlinks

follow symlinks when processing in place

-i[SUFFIX], --in-place[=SUFFIX]

edit files in place (makes backup if extension supplied)

-l N, --line-length=N

specify the desired line-wrap length for the ’l’ command

--posix

disable all GNU extensions.

-r, --regexp-extended

use extended regular expressions in the script.

-s, --separate

consider files as separate rather than as a single continuous long stream.

-u, --unbuffered

load minimal amounts of data from the input files and flush the output buffers more often

--help

display this help and exit

--version

output version information and exit

If no -e, --expression, -f, or --file option is given, then the first non-option argument is taken as the sed script to interpret. All remaining arguments are names of input files; if no input files are specified, then the standard input is read.

GNU sed home page: <http://www.gnu.org/software/sed/>. General help using GNU software: <http://www.gnu.org/gethelp/>. E-mail bug reports to: <bug-gnu-utils[:at:]gnu[:dot:]org>. Be sure to include the word ’’sed’’ somewhere in the ’’Subject:’’ field.

addresses

Sed commands can be given with no addresses, in which case the command will be executed for all input lines; with one address, in which case the command will only be executed for input lines which match that address; or with two addresses, in which case the command will be executed for all input lines which match the inclusive range of lines starting from the first address and continuing to the second address. Three things to note about address ranges: the syntax is addr1,addr2 (i.e., the addresses are separated by a comma); the line which addr1 matched will always be accepted, even if addr2 selects an earlier line; and if addr2 is a regexp, it will not be tested against the line that addr1 matched.

After the address (or address-range), and before the command, a ! may be inserted, which specifies that the command shall only be executed if the address (or address-range) does not match.

The following address types are supported:

number

Match only the specified line number.

first~step

Match every step’th line starting with line first. For example, ’’sed -n 1~2p’’ will print all the odd-numbered lines in the input stream, and the address 2~5 will match every fifth line, starting with the second. first can be zero; in this case, sed operates as if it were equal to step. (This is an extension.)

$

Match the last line.

/regexp/

Match lines matching the regular expression regexp.

\cregexpc

Match lines matching the regular expression regexp. The c may be any character.

GNU sed also supports some special 2-address forms:
0,addr2

Start out in "matched first address" state, until addr2 is found. This is similar to 1,addr2, except that if addr2 matches the very first line of input the 0,addr2 form will be at the end of its range, whereas the 1,addr2 form will still be at the beginning of its range. This works only when addr2 is a regular expression.

addr1,+N

Will match addr1 and the N lines following addr1.

addr1,~N

Will match addr1 and the lines following addr1 until the next line whose input line number is a multiple of N.

command synopsis

This is just a brief synopsis of sed commands to serve as a reminder to those who already know sed; other documentation (such as the texinfo document) must be consulted for fuller descriptions.

Zero-address ’’commands’’
label

Label for b and t commands.

#comment

The comment extends until the next newline (or the end of a -e script fragment).

}

The closing bracket of a { } block.

Zero- or One- address commands

=

Print the current line number.

a \

text

Append text, which has each embedded newline preceded by a backslash.

i \

text

Insert text, which has each embedded newline preceded by a backslash.

q [exit-code]

Immediately quit the sed script without processing any more input, except that if auto-print is not disabled the current pattern space will be printed. The exit code argument is a GNU extension.

Q [exit-code]

Immediately quit the sed script without processing any more input. This is a GNU extension.

filename

Append text read from filename.

filename

Append a line read from filename. Each invocation of the command reads a line from the file. This is a GNU extension.

Commands which accept address ranges

{

Begin a block of commands (end with a }).

label

Branch to label; if label is omitted, branch to end of script.

c \

text

Replace the selected lines with text, which has each embedded newline preceded by a backslash.

d

Delete pattern space. Start next cycle.

D

Delete up to the first embedded newline in the pattern space. Start next cycle, but skip reading from the input if there is still data in the pattern space.

h H

Copy/append pattern space to hold space.

g G

Copy/append hold space to pattern space.

l

List out the current line in a ’’visually unambiguous’’ form.

width

List out the current line in a ’’visually unambiguous’’ form, breaking it at width characters. This is a GNU extension.

n N

Read/append the next line of input into the pattern space.

p

Print the current pattern space.

P

Print up to the first embedded newline of the current pattern space.

s/regexp/replacement/

Attempt to match regexp against the pattern space. If successful, replace that portion matched with replacement. The replacement may contain the special character & to refer to that portion of the pattern space which matched, and the special escapes \1 through \9 to refer to the corresponding matching sub-expressions in the regexp.

label

If a s/// has done a successful substitution since the last input line was read and since the last t or T command, then branch to label; if label is omitted, branch to end of script.

label

If no s/// has done a successful substitution since the last input line was read and since the last t or T command, then branch to label; if label is omitted, branch to end of script. This is a GNU extension.

filename

Write the current pattern space to filename.

filename

Write the first line of the current pattern space to filename. This is a GNU extension.

x

Exchange the contents of the hold and pattern spaces.

y/source/dest/

Transliterate the characters in the pattern space which appear in source to the corresponding character in dest.

copyright

Copyright © 2009 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, to the extent permitted by law.

GNU sed home page: <http://www.gnu.org/software/sed/>. General help using GNU software: <http://www.gnu.org/gethelp/>. E-mail bug reports to: <bug-gnu-utils[:at:]gnu[:dot:]org>. Be sure to include the word ’’sed’’ somewhere in the ’’Subject:’’ field.

regular expressions

POSIX.2 BREs should be supported, but they aren’t completely because of performance problems. The \n sequence in a regular expression matches the newline character, and similarly for \a, \t, and other sequences.


bugs

E-mail bug reports to bonzini[:at:]gnu[:dot:]org. Be sure to include the word ’’sed’’ somewhere in the ’’Subject:’’ field. Also, please include the output of ’’sed --version’’ in the body of your report if at all possible.


see also

awk , ed , grep , tr , perlre, sed.info, any of various books on sed, the sed FAQ (http://sed.sf.net/grabbag/tutorials/sedfaq.txt), http://sed.sf.net/grabbag/.

The full documentation for sed is maintained as a Texinfo manual. If the info and sed programs are properly installed at your site, the command

info sed

should give you access to the complete manual.

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