fast, line-wise "grep -n" equivalent for unix directory structure

You might wish to investigate the GNU idutils toolkit. On a local copy of the Linux kernel sources, it can give output like this:

$ gid ugly
include / linux / hil_mlc.h: 66: * a positive
return value causes the "ugly"
branch to be taken.
include / linux / hil_mlc.h: 101: int ugly; /* Node to jump to on timeout       */

Rebuilding the index from a cold cache is reasonably quick:

$ time mkid

real 1 m33 .022 s
user 0 m17 .360 s
sys 0 m2 .730 s

Rebuilding the index from a warm cache is much faster:

$ time mkid

real 0 m15 .692 s
user 0 m15 .070 s
sys 0 m0 .520 s

On a cold cache, git grep foo (which returned 1656 entries, far more than idutils):

$ time git grep foo > /dev/null

real 0 m19 .231 s
user 0 m1 .480 s
sys 0 m0 .680 s

Once the cache was warm, git grep foo runs much faster:

$ time git grep foo > /dev/null

real 0 m0 .264 s
user 0 m1 .320 s
sys 0 m0 .330 s

The command line client works like this:

ws - update - b--index my.idx datadir # build the index
ws - update - b--append--index my.idx datadir # incremental update
ws--index my.idx hello world # query the index

Suggestion : 2

copy text with space to enter visual mode, then select text, then use y to yank, then hit Enter,An Introduction to the Command-Line (on Unix-like systems) - Using the Python Shell to do Math

command - f
command--flag

Suggestion : 3

adding contents of file r for entire file R for line by line ,This filtering is much like using grep, head and tail commands in many ways and there are even more features Use sed for inplace editing, the filtered lines to be transformed etc. Not as substitute for those commands ,By default, sed prints every input line, including any changes made by commands like substitution printing here refers to line being part of sed output which may be shown on terminal, redirected to file, etc ,Use sed for inplace editing, the filtered lines to be transformed etc. Not as substitute for those commands

$ sed--version | head - n1
sed(GNU sed) 4.2 .2

$ man sed
SED(1) User Commands SED(1)

NAME
sed - stream editor
for filtering and transforming text

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

   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.
   ...

Detailed examples for substitute command will be covered in later sections, syntax is

s / REGEXP / REPLACEMENT / FLAGS

editing stdin

$ # sample command output to be edited
$ seq 10 | paste - sd,
   1, 2, 3, 4, 5, 6, 7, 8, 9, 10

$ # change only first ','
to ' : '
$ seq 10 | paste - sd, | sed 's/,/ : /'
1: 2, 3, 4, 5, 6, 7, 8, 9, 10

$ # change all ','
to ' : '
by using 'g'
modifier
$ seq 10 | paste - sd, | sed 's/,/ : /g'
1: 2: 3: 4: 5: 6: 7: 8: 9: 10

When extension is given, the original input file is preserved with name changed according to extension provided

$ # '.bkp'
is extension provided
$ sed - i.bkp 's/Hi/Hello/'
greeting.txt
$ # output from sed is written back to 'greeting.txt'
$ cat greeting.txt
Hello there
Have a nice day

$ # original file is preserved in 'greeting.txt.bkp'
$ cat greeting.txt.bkp
Hi there
Have a nice day

Use this option with caution, changes made cannot be undone

$ sed - i 's/nice day/safe journey/'
greeting.txt

$ # note, 'Hi'
was already changed to 'Hello' in previous example
$ cat greeting.txt
Hello there
Have a safe journey