`/` is not _the_ delimiter in `sed` commands, it&#39;s just one of the possible ones. For this example, you can for example use `,` instead since it does not conflict with your strings;

    echo &#39;I think http://www.find.com/page is my favorite&#39; | 
        sed &#39;s,http://www.find.com/page,http://www.replace.com/page,g&#39;

`sed` can take whatever follows the &quot;s&quot; as the separator. Since you are working with `URL` it is a good practice to use a different delimiter other than `/` to not confuse `sed` when your substitution ends and replacement begins. 

However, having said that you can definitely use `/` if you wish too. You just need to escape the literal `/`.

So, you can either do:

    sed &#39;s/http:\/\/www.find.com\/page/http:\/\/www.replace.com\/page/g&#39; input_file

or use a different delimiter to avoid making your cryptic sed more cryptic. 

    sed &#39;s#http://www.find.com/page#http://www.replace.com/page#g&#39; input_file


What is the best way to implement global counters for a highly concurrent application?  In my case I may have 10K-20K go routines performing &quot;work&quot;, and I want to count the number and types of items that the routines are working on collectively...

The &quot;classic&quot; synchronous coding style would look like:


    var work_counter int

    func GoWorkerRoutine() {
        for {
            // do work
            atomic.AddInt32(&amp;work_counter,1)
        }    
    }

Now this gets more complicated because I want to track the &quot;type&quot; of work being done, so really I&#39;d need something like this:

    var work_counter map[string]int
    var work_mux sync.Mutex

    func GoWorkerRoutine() {
        for {
            // do work
            work_mux.Lock()
            work_counter[&quot;type1&quot;]++
            work_mux.Unlock()
        }    
    }

It seems like there should be a &quot;go&quot; optimized way using channels or something similar to this:

    var work_counter int
    var work_chan chan int // make() called somewhere else (buffered)

    // started somewher else
    func GoCounterRoutine() {
        for {
            select {
                case c := &lt;- work_chan:
                    work_counter += c
                    break
            }
        }
    }

    func GoWorkerRoutine() {
        for {
            // do work
            work_chan &lt;- 1
        }    
    }

This last example is still missing the map, but that&#39;s easy enough to add.  Will this style provide better performance than just a simple atomic increment?  I can&#39;t tell if this is more or less complicated when we&#39;re talking about concurrent access to a global value versus something that may block on I/O to complete...

Thoughts are appreciated.

Update 5/28/2013:

I tested a couple implementations, and the results were not what I expected, here&#39;s my counter source code:

    package helpers
    
    import (
    )
    
    type CounterIncrementStruct struct {
    	bucket string
    	value int
    }
    
    type CounterQueryStruct struct {
    	bucket string
    	channel chan int
    }
    
    var counter map[string]int
    var counterIncrementChan chan CounterIncrementStruct
    var counterQueryChan chan CounterQueryStruct
    var counterListChan chan chan map[string]int
    
    func CounterInitialize() {
    	counter = make(map[string]int)
    	counterIncrementChan = make(chan CounterIncrementStruct,0)
    	counterQueryChan = make(chan CounterQueryStruct,100)
    	counterListChan = make(chan chan map[string]int,100)
    	go goCounterWriter()
    }
    
    func goCounterWriter() {
    	for {
    		select {
    			case ci := &lt;- counterIncrementChan:
    				if len(ci.bucket)==0 { return }
    				counter[ci.bucket]+=ci.value
    				break
    			case cq := &lt;- counterQueryChan:
    				val,found:=counter[cq.bucket]
    				if found {
    					cq.channel &lt;- val
    				} else {
    					cq.channel &lt;- -1	
    				}
    				break
    			case cl := &lt;- counterListChan:
    				nm := make(map[string]int)
    				for k, v := range counter {
    				    nm[k] = v
    				}
    				cl &lt;- nm
    				break
    		}
    	}
    }
    
    func CounterIncrement(bucket string, counter int) {
    	if len(bucket)==0 || counter==0 { return }
    	counterIncrementChan &lt;- CounterIncrementStruct{bucket,counter}
    }
    
    func CounterQuery(bucket string) int {
    	if len(bucket)==0 { return -1 }
    	reply := make(chan int)
    	counterQueryChan &lt;- CounterQueryStruct{bucket,reply}
    	return &lt;- reply
    }
    
    func CounterList() map[string]int {
    	reply := make(chan map[string]int)
    	counterListChan &lt;- reply
    	return &lt;- reply
    }

It uses channels for both writes and reads which seems logical.

Here are my test cases:

    func bcRoutine(b *testing.B,e chan bool) {
    	for i := 0; i &lt; b.N; i++ {
    		CounterIncrement(&quot;abc123&quot;,5)
    		CounterIncrement(&quot;def456&quot;,5)
    		CounterIncrement(&quot;ghi789&quot;,5)
    		CounterIncrement(&quot;abc123&quot;,5)
    		CounterIncrement(&quot;def456&quot;,5)
    		CounterIncrement(&quot;ghi789&quot;,5)
    	}
    	e&lt;-true
    }
    
    func BenchmarkChannels(b *testing.B) {
    	b.StopTimer()
    	CounterInitialize()
    	e:=make(chan bool)
    	b.StartTimer()
    	
    	go bcRoutine(b,e)
    	go bcRoutine(b,e)
    	go bcRoutine(b,e)
    	go bcRoutine(b,e)
    	go bcRoutine(b,e)
    	
    	&lt;-e
    	&lt;-e
    	&lt;-e
    	&lt;-e
    	&lt;-e
    	
    }
    
    var mux sync.Mutex
    var m map[string]int
    func bmIncrement(bucket string, value int) {
    	mux.Lock()
    	m[bucket]+=value
    	mux.Unlock()
    }
    
    func bmRoutine(b *testing.B,e chan bool) {
    	for i := 0; i &lt; b.N; i++ {
    		bmIncrement(&quot;abc123&quot;,5)
    		bmIncrement(&quot;def456&quot;,5)
    		bmIncrement(&quot;ghi789&quot;,5)
    		bmIncrement(&quot;abc123&quot;,5)
    		bmIncrement(&quot;def456&quot;,5)
    		bmIncrement(&quot;ghi789&quot;,5)
    	}
    	e&lt;-true
    }
    
    func BenchmarkMutex(b *testing.B) {
    	b.StopTimer()
    	m=make(map[string]int)
    	e:=make(chan bool)
    	b.StartTimer()
    	
    	for i := 0; i &lt; b.N; i++ {
    		bmIncrement(&quot;abc123&quot;,5)
    		bmIncrement(&quot;def456&quot;,5)
    		bmIncrement(&quot;ghi789&quot;,5)
    		bmIncrement(&quot;abc123&quot;,5)
    		bmIncrement(&quot;def456&quot;,5)
    		bmIncrement(&quot;ghi789&quot;,5)
    	}
    	
    	go bmRoutine(b,e)
    	go bmRoutine(b,e)
    	go bmRoutine(b,e)
    	go bmRoutine(b,e)
    	go bmRoutine(b,e)
    	
    	&lt;-e
    	&lt;-e
    	&lt;-e
    	&lt;-e
    	&lt;-e
    	
    }

I implemented a simple benchmark with just a mutex around the map (just testing writes), and benchmarked both with 5 goroutines running in parallel.  Here are the results:

    $ go test --bench=. helpers
    PASS
    BenchmarkChannels         100000             15560 ns/op
    BenchmarkMutex   1000000              2669 ns/op
    ok      helpers 4.452s

I would not have expected the mutex to be that much faster...

Further thoughts?

Best way to implement global counters for highly concurrent applications?

I think it is because the JVM needs to move objects, is that correct?

Why does the JVM full GC need to stop-the-world?

I&#39;m attempting to use SED through OS X Terminal to perform a find and replace.

Imagine I have this string littered throughout the text file: http://www.find.com/page

And I want to replace it with this string: http://www.replace.com/page

I&#39;m having trouble because I&#39;m not sure how to properly escape or use the &quot;/&quot; character in my strings.  For example if I simply wanted to find &quot;cat&quot; and replace with &quot;dog&quot; I&#39;ve found the following command that works perfectly:

    sed -i &#39;&#39; &#39;s/cat/dog/g&#39; file.txt

Does anyone have any ideas on how to achieve the same functionality only instead of cat and dog have strings or URLs that container the &quot;/&quot; character?  I tried many different ways of escaping the &quot;/&quot; characters but then it seems as if SED can no longer &quot;find&quot; the string and it doesn&#39;t perform any find &amp; replace actions.

Any help or tips are greatly appreciated.

Thanks!

How to use SED to find and replace URL strings with the &quot;/&quot; character in the targeted strings?

I'm attempting to use SED through OS X Terminal to perform a find and replace.
Imagine I have this string littered throughout the text file: <a href="http://www.find.com/page" target="_blank" rel="noopener noreferrer">http://www.find.com/page</a>
And I want to replace it with this string: <a href="http://www.replace.com/page" target="_blank" rel="noopener noreferrer">http://www.replace.com/page</a>
I'm having trouble because I'm not sure how to properly escape or use the "/" character in my strings. For example if I simply wanted to find "cat" and replace with "dog" I've found the following command that works perfectly:
<pre><code class="hljs language-bash">sed -i '' 's/cat/dog/g' file.txt
</code></pre>
Does anyone have any ideas on how to achieve the same functionality only instead of cat and dog have strings or URLs that container the "/" character? I tried many different ways of escaping the "/" characters but then it seems as if SED can no longer "find" the string and it doesn't perform any find &#x26; replace actions.
Any help or tips are greatly appreciated.
Thanks!

I have created a `.pgpass` file in my home directory which looks like this

`localhost:5432:somedb:someuser:somepass`

I am using a shell script which creates a directory and puts a pg_dump of `somedb` there :

    mkdir directory
    pg_dump somedb &gt; directory/somefile.dump

It still prompts for the password.
 
Where is the mistake here ?

postgresql: .pgpass not working

I&#39;m trying to find the files existing in one directory but not in the other, I tried to use this command:

    diff -q dir1 dir2

The problem with the above command that it finds both the files in `dir1` but not in `dir2` as well as the files in `dir2` but not in `dir1`, 

I am trying to find the files in `dir1` but not in `dir2` only.

Here&#39;s a small sample of what my data looks like

    dir1    dir2    dir3
    1.txt   1.txt   1.txt
    2.txt   3.txt   3.txt
    5.txt   4.txt   5.txt
    6.txt   7.txt   8.txt

Another question on my mind is how can I find the files in `dir1` but not in `dir2` or `dir3` in a single command?

Find the files existing in one directory but not in the other

I&#39;m curious as to why the backspace is necessary when setting IFS to split on newlines like this:

    IFS=$(echo -en &quot;\n\b&quot;)

Why can I not just use this (which doesn&#39;t work) instead?

    IFS=$(echo -en &quot;\n&quot;)

I&#39;m on a Linux system that is saving files with Unix line endings.  I&#39;ve converted my file with newlines to hex and it definitely only uses &quot;0a&quot; as the newline character.

I&#39;ve googled a lot and although many pages document the newline followed by backspace solution, none that I have found explain why the backspace is required.

-David.


When setting IFS to split on newlines, why is it necessary to include a backspace?

I am trying to redirect all output from a command line programme to a file.  I am using Bash.  Some of the output is directed to a the file, but some still appears in the terminal and is not stored to the file.  

Similar symptoms are described here:

https://stackoverflow.com/questions/6674327/redirect-all-output-to-file

However I have tried the proposed solution (capture stderr) without success:

    &lt;cmd&gt; &lt;args&gt; &gt; stdout.txt 2&gt; stderr.txt

The file stderr.txt is created but is empty.

A possible clue is that the command-line programme is a client communicating with a server on the same machine.  It may be that some of the output is coming from the **server**.  

Is there a way to capture all the output from the terminal, irrespective of its origin?

**EDIT:**

I&#39;ve confirmed that the missing output is generated by the server.  Running the command in a separate terminal causes some output in both terminals, I can pipe all the output from the command terminal to a file.  This raises issues about how to capture the server output, but that&#39;s a different question.


Redirect all output to file using Bash on Linux?

In the following program, if I set the variable `$foo` to the value 1 inside the first `if` statement, it works in the sense that its value is remembered after the if statement. However, when I set the same variable to the value 2 inside an `if` which is inside a `while` statement, it&#39;s forgotten after the `while` loop. It&#39;s behaving like I&#39;m using some sort of copy of the variable `$foo` inside the `while` loop and I am modifying only that particular copy. Here&#39;s a complete test program:

    #!/bin/bash
    
    set -e
    set -u 
    foo=0
    bar=&quot;hello&quot;  
    if [[ &quot;$bar&quot; == &quot;hello&quot; ]]
    then
        foo=1
        echo &quot;Setting \$foo to 1: $foo&quot;
    fi

    echo &quot;Variable \$foo after if statement: $foo&quot;   
    lines=&quot;first line\nsecond line\nthird line&quot; 
    echo -e $lines | while read line
    do
        if [[ &quot;$line&quot; == &quot;second line&quot; ]]
        then
    	foo=2
    	echo &quot;Variable \$foo updated to $foo inside if inside while loop&quot;
        fi
        echo &quot;Value of \$foo in while loop body: $foo&quot;
    done
    
    echo &quot;Variable \$foo after while loop: $foo&quot;
    
    # Output:
    # $ ./testbash.sh
    # Setting $foo to 1: 1
    # Variable $foo after if statement: 1
    # Value of $foo in while loop body: 1
    # Variable $foo updated to 2 inside if inside while loop
    # Value of $foo in while loop body: 2
    # Value of $foo in while loop body: 2
    # Variable $foo after while loop: 1
    
    # bash --version
    # GNU bash, version 4.1.10(4)-release (i686-pc-cygwin)

A variable modified inside a while loop is not remembered

I have a Visual Studio project, which is developed locally. Code files have to be deployed to a remote server. The only problem are the URLs they contain, which are hard-coded.

The project contains URLS such as `?page=one`. For the link to be valid on the server, it must be `/page/one` .

I&#39;ve decided to replace all URLS in my code files with sed before deployment, but I&#39;m stuck on slashes.

I know this is a not a pretty solution, but it&#39;s simple and would save me a lot of time. The total number of strings I have to replace is fewer than 10. Total number of files which have to be checked is ~30.

Example describing my situation is below:

Command I&#39;m using:

    sed -f replace.txt &lt; a.txt &gt; b.txt

`replace.txt` which contains all the strings:

    s/?page=one&amp;/pageone/g
    s/?page=two&amp;/pagetwo/g
    s/?page=three&amp;/pagethree/g

`a.txt`:

    ?page=one&amp;
    ?page=two&amp;
    ?page=three&amp;

Content of `b.txt` after I run my sed command:

    pageone
    pagetwo
    pagethree

What I want `b.txt` to contain:

    /page/one
    /page/two
    /page/three

How to insert strings containing slashes with sed?

Is there an elegant method in bash for running `grep` against a text file with two or more patterns, and each pattern that matches is output in a different color?  

So a line that matches on `MALE` and `AUGUST` would output `MALE` in blue and `AUGUST` in orange?
I am open to the use of `sed`, `awk`, `grep` and crayons or others.



Grep output with multiple Colors?

I&#39;m using sed to filter a list of files. I have a sorted list of folders and I want to get all lines after a specific one. To do this task I&#39;m using the solution described [here](https://stackoverflow.com/a/5935779/518204) which works pretty well with any input I tried but it doesn&#39;t work when the match is on the first line. In that case sed will remove all lines of the input

Here it&#39;s an example:

    $ ls -1 /
    bin
    boot
    ...
    sys
    tmp
    usr
    var
    vmlinuz
    
    $ ls -1 / | sed &#39;1,/tmp/d&#39;
    usr
    var
    vmlinuz
    
    $ ls -1 / | sed &#39;1,/^bin$/d&#39;
    # sed will delete all lines from the input stream

How should I change the command to consider also the limit case when first line is matched by regexp?

BTW `sed &#39;1,1d&#39;` correctly works and remove the first line only.

Remove all lines before a match with sed

I want to grab the last two numbers (one int, one float; followed by optional whitespace) and print only them.

Example:
   
    foo bar &lt;foo&gt; bla 1 2 3.4

Should print:
    
    2 3.4

So far, I have the following:

    sed -n  &#39;s/$[0-9][0-9]*[\ \t][0-9.]*[\ \t]*$$/replacement/p&#39; 

will give me

    foo bar &lt;foo&gt; bla 1 replacement

However, if I try to replace it with group 1, the whole line is printed.

    sed -n  &#39;s/$[0-9][0-9]*[\ \t][0-9.]*[\ \t]*$$/\1/p&#39; 



How can I print only the section of the line that matches the regex in the group?

sed: print only matching group

I want to run a simple command of replacing absolute paths to relative ones inside a CSS file like this:

    sed -i &#39;s/\/fonts/../fonts/&#39; /Users/sergeybasharov/WebstormProjects/snap/compiled/Content/stylesheets/style.css

It throws this

    sed: 1: &quot;/Users/sergeybasharov/W ...&quot;: bad flag in substitute command: &#39;b&#39;

What can be wrong in this simple script?

sed throws &#39;bad flag in substitute command&#39;

On GitHub I want to build a table containing pieces of code in Markdown. It works fine except when I put a pipe char (i.e. | ) between the backtick (i.e. ` ) chars.

Here is what I want:

          a     |  r  
    ------------|-----
     `a += x;`  |  r1
     `a |= y;`  |  r2

The problem is that the vertical bar in the code statement of the second line is interpreted as a column delimiter. Then the table rendering looks pretty ugly. How could I avoid that?

Note that I already tried to use the `&amp;#124;` HTML code, but it produces `a &amp;#124;= y;`.



How to escape a pipe char in a code statement in a markdown table?

I just upgraded Git. I&#39;m on Git version 1.8.3.

This morning I tried to unstash a change 1 deep in the stack.

I ran `git stash pop stash@{1}` and got this error.

    

&gt; fatal: ambiguous argument &#39;stash@1&#39;: unknown revision or path not in
&gt; the working tree.
&gt;     Use &#39;--&#39; to separate paths from revisions, like this:
&gt;     &#39;git &lt;command&gt; [&lt;revision&gt;...] -- [&lt;file&gt;...]&#39;

I&#39;ve tried about 20+ variations on this as well as using `apply` instead of `pop` with no success. What&#39;s changed? Anyone else encounter this?

How to Git stash pop specific stash in 1.8.3?

I am trying to execute the following line in Command Prompt:

    curl -X POST -d &#39;{ &quot;method&quot; : &quot;account_info&quot;, &quot;params&quot; : [ { &quot;account&quot; : &quot;rHb9CJAWyB4rj91VRWn96DkukG4bwdtyTh&quot;} ] }&#39; http://s1.ripple.com:51234

However, I get the following:

    curl: (6) Could not resolve host: method
    curl: (7) Failed connect to :80; No error
    curl: (6) Could not resolve host: account_info,
    curl: (6) Could not resolve host: params
    curl: (7) Failed connect to :80; No error
    curl: (3) [globbing] illegal character in range specification at pos 2
    curl: (3) [globbing] unmatched brace at pos 2
    curl: (6) Could not resolve host: account
    curl: (7) Failed connect to :80; No error
    curl: (3) [globbing] unmatched close brace/bracket at pos 35
    curl: (3) [globbing] unmatched close brace/bracket at pos 1
    curl: (3) [globbing] unmatched close brace/bracket at pos 1
    unable to parse request

I am on Windows, and the error has to do with quotes, braces, and globbing. I tried escaping quotes by preceding them with a backslash, with no luck.

Having trouble escaping quotes and braces

I am looking for an efficient way to convert back slash to forward slash in R. Sometime I copy the link of the directory in Windows and I get something like this:

`C:\Users\jd\Documents\folder\file.txt`

How can I quickly change this to `C:/Users/jd/Documents/folder/file.txt` ? I cannot even read the above expression as character. It throws an error 

&gt;&quot;\u used without hex digits in character string starting &quot;&quot;C:\u&quot;.

I know TAB function in R helps to find the location fast, but was just wondering if there was any other work around. I could change the working directory to the location of folder also. I was just playing around and tried to convert backslash to forward slash and was not straight forward so asked this just because of curiosity.

Efficiently convert backslash to forward slash in R

I have a line like this in my CSV:

`&quot;Samsung U600 24&quot;&quot;,&quot;10000003409&quot;,&quot;1&quot;,&quot;10000003427&quot;`

Quote next to `24` is used to express inches, while the quote just next to that quote closes the field. I&#39;m reading the line with `fgetcsv` but the parser makes a mistake and reads the value as:

`Samsung U600 24&quot;,10000003409&quot;`

I tried putting a backslash before the inches quote, but then I just get a backslash in the name:

`Samsung U600 24\&quot;`

Is there a way to properly escape this in the CSV, so that the value would be `Samsung U600 24&quot;` , or do I have to regex it in the processor?

Content Type	Original Author	Original Content on Stackoverflow
Question	LearnWebCode	View Question on Stackoverflow
Solution 1 - Bash	Joachim Isaksson	View Answer on Stackoverflow
Solution 2 - Bash	jaypal singh	View Answer on Stackoverflow

How to use SED to find and replace URL strings with the "/" character in the targeted strings?

Bash Problem Overview

Bash Solutions

Solution 1 - Bash

Solution 2 - Bash

Why does the JVM full GC need to stop-the-world?

Best way to implement global counters for highly concurrent applications?

Attributions