Check whether a given string exists in a file

[kd]

Hi All,

Is there a command to check whether a given string is present in a text
file, without having to read the contents of the file, a line at a time and
then check for the given string?

Thanks.
kd

[Herfried K. Wagner [MVP]]

"kd" <kd@discussions .microsoft.com> schrieb:

Is there a command to check whether a given string is present in a text
file, without having to read the contents of the file, a line at a time
and
then check for the given string?

No. You can use 'ReadToEnd' to read the whole file into a string and use
'InStr' to check for the pattern, but this is only recommended for small
files.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

[Diana Mueller]

"kd" <kd@discussions .microsoft.com> schrieb im Newsbeitrag
news:93******** *************** ***********@mic rosoft.com...

Is there a command to check whether a given string is present in a text
file, without having to read the contents of the file, a line at a time and then check for the given string?

Well, you could do something like

Private Function FindInFile(ByVa l searchPattern As String, ByVal path As
String) As Boolean
Dim sr As IO.StreamReader
Try
sr = New IO.StreamReader (IO.File.OpenRe ad(path))
Return (sr.ReadToEnd.I ndexOf(searchPa ttern) > -1)
Catch ex As Exception
Return Nothing
Finally
sr.Close()
End Try
End Function

but I doubt that this would be faster then checking line by line and
breaking if a match occurs. That could be easily tested though...

[Cor Ligthert]

KD,

Do you mean with text "text" or ".txt". Because the answers you have got now
are for ".txt".
For "text" there is not *one* method, because you don't know the format of
the saved file.

I hope this helps?

Cor

[kd]

Thanks

What would you suggest the recommended size of the .txt file, in order to use
'ReadToEnd'?

kd
"Herfried K. Wagner [MVP]" wrote:

"kd" <kd@discussions .microsoft.com> schrieb:

Is there a command to check whether a given string is present in a text
file, without having to read the contents of the file, a line at a time
and
then check for the given string?

No. You can use 'ReadToEnd' to read the whole file into a string and use
'InStr' to check for the pattern, but this is only recommended for small
files.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

[kd]

Thanks for the code.

kd

"Diana Mueller" wrote:

"kd" <kd@discussions .microsoft.com> schrieb im Newsbeitrag
news:93******** *************** ***********@mic rosoft.com...

Is there a command to check whether a given string is present in a text
file, without having to read the contents of the file, a line at a time

and

then check for the given string?

Well, you could do something like

Private Function FindInFile(ByVa l searchPattern As String, ByVal path As
String) As Boolean
Dim sr As IO.StreamReader
Try
sr = New IO.StreamReader (IO.File.OpenRe ad(path))
Return (sr.ReadToEnd.I ndexOf(searchPa ttern) > -1)
Catch ex As Exception
Return Nothing
Finally
sr.Close()
End Try
End Function

but I doubt that this would be faster then checking line by line and
breaking if a match occurs. That could be easily tested though...

[kd]

It is a .txt file.
kd

"Cor Ligthert" wrote:

KD,

Do you mean with text "text" or ".txt". Because the answers you have got now
are for ".txt".
For "text" there is not *one* method, because you don't know the format of
the saved file.

I hope this helps?

Cor

[kd]

I mean what would be the maximum size that you suggest for the .txt file in
order to use 'ReadToEnd'?

kd

"kd" wrote:

Thanks

What would you suggest the recommended size of the .txt file, in order to use
'ReadToEnd'?

kd
"Herfried K. Wagner [MVP]" wrote:

"kd" <kd@discussions .microsoft.com> schrieb:

Is there a command to check whether a given string is present in a text
file, without having to read the contents of the file, a line at a time
and
then check for the given string?

No. You can use 'ReadToEnd' to read the whole file into a string and use
'InStr' to check for the pattern, but this is only recommended for small
files.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

[Herfried K. Wagner [MVP]]

"kd" <kd@discussions .microsoft.com> schrieb:

I mean what would be the maximum size that you suggest for the .txt file
in
order to use 'ReadToEnd'?

Some KB :-). Note that the file will be loaded into memory and thus the
memory usage will be incremented by at least the size of the file.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

[Herfried K. Wagner [MVP]]

Addendum:

Code for reading a file line-by-line:

Reading a text file line-by-line or blockwise with a progress indicator
<URL:http://dotnet.mvps.org/dotnet/faqs/?id=readfile&la ng=en>

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>