Use `-f` with a single dash to denote the standard input:

    $ echo Content | grep -f - notice.html 
    &lt;meta http-equiv=&quot;Content-Type&quot; content=&quot;text/html; charset=ISO-8859-1&quot;&gt;
    ...

Note: This has been tested with GNU grep - I am not sure if it&#39;s specified by POSIX.



I am uploading a file in php and only want to upload it if it&#39;s a csv file. I believe my syntax is right for the content type. It always goes to else statement when it&#39;s a csv file. What I am doing wrong here?

    if (($_FILES[&quot;file&quot;][&quot;type&quot;] == &quot;text/csv&quot;))
    {
    
    }
    else
    {
    
    }

If I change the content type it works for that format just not csv.

Check file uploaded is in csv format

Of all the Instruments Trace Templates, I love using:

* Zombies to detect where an object is getting over-released, great for debugging `EXEC_BAD_ACCESS` errors.
* Leaks to detect memory leaks.
* Core Animation w Color Blended Layers to detect frame rate &amp; translucent subviews, great for smoothing up `UITableView` scrolling.

I always hear people saying to profile my app&#39;s memory usage &amp; performance.

1. Why should I profile memory usage &amp; performance? My app runs fine.
2. How do I do it?

I&#39;ve used Allocations and see that my iPhone app starts at 1 MB total allocated memory and grows to 5 MB after normal usage. What is too high amount of memory usage on the iPhone? iPad? Mac?

How to profile memory usage &amp; performance with Instruments?

How can I make grep read the **expression** from standard input (stdin)?

For example (the following doesn&#39;t work):

    grep -i -f &amp;0 /path/to/text/file &lt; &quot;/regexp/&quot;


Read expression for grep from standard input

How can I make grep read the expression from standard input (stdin)?
For example (the following doesn't work):
<pre><code class="hljs language-vbnet">grep -i -f &#x26;0 /path/to/text/file &#x3C; "/regexp/"
</code></pre>

I&#39;m trying to add a line of text to the middle of a text file in a bash script.  Specifically I&#39;m trying add a nameserver to my /etc/resolv.conf file.  As it stands, resolv.conf looks like this:

    # Generated by NetworkManager
    domain dhcp.example.com
    search dhcp.example.com
    nameserver 10.0.0.1
    nameserver 10.0.0.2
    nameserver 10.0.0.3

My goal is to add `nameserver 127.0.0.1` above all other nameserver lines, but below any text above that.  In the end I want to my resolve.conf file to look like this:

    # Generated by NetworkManager
    domain dhcp.example.com
    search dhcp.example.com
    nameserver 127.0.0.1
    nameserver 10.0.0.1
    nameserver 10.0.0.2
    nameserver 10.0.0.3

How is this possible via a bash script?  Is this something sed or awk can do?  Or would creative greping to recreate the file be my best move?

How do I add a line of text to the middle of a file using bash?

The following is a sample of a large file named AT5G60410.gff:

    Chr5	TAIR10	gene	24294890	24301147	.	+	.	ID=AT5G60410;Note=protein_coding_gene;Name=AT5G60410
    Chr5	TAIR10	mRNA	24294890	24301147	.	+	.	ID=AT5G60410.1;Parent=AT5G60410;Name=AT5G60410.1;Index=1
    Chr5	TAIR10	protein	24295226	24300671	.	+	.	ID=AT5G60410.1-Protein;Name=AT5G60410.1;Derives_from=AT5G60410.1
    Chr5	TAIR10	exon	24294890	24295035	.	+	.	Parent=AT5G60410.1
    Chr5	TAIR10	five_prime_UTR	24294890	24295035	.	+	.	Parent=AT5G60410.1
    Chr5	TAIR10	exon	24295134	24295249	.	+	.	Parent=AT5G60410.1
    Chr5	TAIR10	five_prime_UTR	24295134	24295225	.	+	.	Parent=AT5G60410.1
    Chr5	TAIR10	CDS	24295226	24295249	.	+	0	Parent=AT5G60410.1,AT5G60410.1-Protein;
    Chr5	TAIR10	exon	24295518	24295598	.	+	.	Parent=AT5G60410.1

I am having some trouble extracting specific lines from this using grep.  I wanted to extract all lines that are of type &quot;gene&quot; or type &quot;exon&quot;, specified in the third column. I was suprised when this did not work:
    
    grep &#39;gene|exon&#39; AT5G60410.gff

No results are returned. Where have I gone wrong?


grepping using the &quot;|&quot; alternative operator

This does not generate any output. How come?

    $ echo &#39;this 1 2 3&#39; | grep &#39;\d\+&#39;

But these do:

    $ echo &#39;this 1 2 3&#39; | grep &#39;\s\+&#39;
    this 1 2 3
    
    $ echo &#39;this 1 2 3&#39; | grep &#39;\w\+&#39;
    this 1 2 3


Is \d not supported by grep&#39;s basic expressions?

I have a file that possibly contains bad formatting (in this case, the occurrence of the pattern `\\backslash`). I would like to use `grep` to return only the line numbers where this occurs (as in, the match was here, go to line # x and fix it).

However, there doesn&#39;t seem to be a way to print the line number (`grep -n`) and not the match or line itself.

I can use another regex to extract the line numbers, but I want to make sure grep cannot do it by itself. `grep -no` comes closest, I think, but still displays the match.

Use grep to report back only line numbers

I have a file with about 1000 lines. I want the part of my file after the line which matches my grep statement.

That is:

    cat file | grep &#39;TERMINATE&#39;     # It is found on line 534

So, I want the file from line 535 to line 1000 for further processing.

How can I do that?



How to get the part of a file after the first line that matches a regular expression

The following Perl script (`my.pl`) can read from either the file in the command line arguments or from [standard input][1] (STDIN):

    while (&lt;&gt;) {
       print($_);
    }

`perl my.pl` will read from standard input, while `perl my.pl a.txt` will read from `a.txt`. This is very handy.

Is there an equivalent in Bash?

  [1]: https://en.wikipedia.org/wiki/Standard_streams#Standard_input_(stdin)


How to read from a file or standard input in Bash

I am reading bunch of integers separated by space or newlines from the standard in using `Scanner(System.in)`.

Is there any faster way of doing this in Java?

What&#39;s the fastest way to read from System.in in Java?

Can someone tell me why this does not work? I&#39;m playing around with file descriptors, but feel a little lost.

    #!/bin/bash
    echo &quot;This&quot;
    echo &quot;is&quot; &gt;&amp;2
    echo &quot;a&quot; &gt;&amp;3
    echo &quot;test.&quot; &gt;&amp;4

The first three lines run fine, but the last two error out. Why?

How do file descriptors work?

I found the very useful syntax

    parser.add_argument(&#39;-i&#39;, &#39;--input-file&#39;, type=argparse.FileType(&#39;r&#39;), default=&#39;-&#39;)

for specifying an input file or using stdin—both of which I want in my program. However, the input file is not always required. If I&#39;m not using `-i` or redirecting input with one of

    $ someprog | my_python_prog
    $ my_python_prog &lt; inputfile

I don&#39;t want my Python program to wait for input. I want it to just move along and use default values.

Optional stdin in Python with argparse

I&#39;m trying to write a Python script that starts a subprocess, and writes to the subprocess stdin. I&#39;d also like to be able to determine an action to be taken if the subprocess crashes.

The process I&#39;m trying to start is a program called `nuke` which has its own built-in version of Python which I&#39;d like to be able to submit commands to, and then tell it to quit after the commands execute. So far I&#39;ve worked out that if I start Python on the command prompt like and then start `nuke` as a subprocess then I can type in commands to `nuke`, but I&#39;d like to be able to put this all in a script so that the master Python program can start `nuke` and then write to its [standard input][1] (and thus into its built-in version of Python) and tell it to do snazzy things, so I wrote a script that starts `nuke` like this:

    subprocess.call([&quot;C:/Program Files/Nuke6.3v5/Nuke6.3&quot;, &quot;-t&quot;, &quot;E:/NukeTest/test.nk&quot;])

Then nothing happens because `nuke` is waiting for user input. How would I now write to standard input?

I&#39;m doing this because I&#39;m running a plugin with `nuke` that causes it to crash intermittently when rendering multiple frames. So I&#39;d like this script to be able to start `nuke`, tell it to do something and then if it crashes, try again. So if there is a way to catch a crash and still be OK then that&#39;d be great.

  [1]: https://en.wikipedia.org/wiki/Standard_streams#Standard_input_.28stdin.29


Content Type	Original Author	Original Content on Stackoverflow
Question	Dor	View Question on Stackoverflow
Solution 1 - Grep	thkala	View Answer on Stackoverflow

Read expression for grep from standard input

Grep Problem Overview

Grep Solutions

Solution 1 - Grep

How to profile memory usage & performance with Instruments?

Check file uploaded is in csv format

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