How to read until EOF from cin in C

Question

I am coding a program that reads data directly from user input and was wondering how could I  without loops  read all data until EOF from standard input  I was considering using cin get  input    0    but   0  is not really the EOF character  that just reads until EOF or   0   whichever comes first   Or is using loops the only way to do it  If so  what is the best way

User · Answer

You can use the std  istream  getline    or preferably the version that works on std  string  function to get an entire line   Both have versions that allow you to specify the delimiter  end of line character    The default for the string version is   n

User · Answer

Using loops    include  lt iostream gt  using namespace std         numbers int n  while  cin  gt  gt  n                lines string line  while  getline cin  line                 characters char c  while  cin get c                resource

User · Answer

while std  cin        do something

User · Answer

while std  cin        do something

User · Answer

One option is to a use a container  e g   std  vector lt char gt  data    and redirect all input into this collection until EOF is received  i e   std  copy std  istream iterator lt char gt  std  cin       std  istream iterator lt char gt         std  back inserter data      However  the used container might need to reallocate memory too often  or you will end with a std  bad alloc exception when your system gets out of memory  In order to solve these problems  you could reserve a fixed amount N of elements and process these amount of elements in isolation  i e   data reserve N       while    some condition is met          std  copy n std  istream iterator lt char gt  std  cin           N          std  back inserter data            process data         data clear

User · Answer

Probable simplest and generally efficient    include  lt iostream gt  int main         std  cout  lt  lt  std  cin rdbuf        If needed  use stream of other types like std  ostringstream as buffer instead of standard output stream here

User · Answer

Using loops    include  lt iostream gt  using namespace std         numbers int n  while  cin  gt  gt  n                lines string line  while  getline cin  line                 characters char c  while  cin get c                resource

User · Answer

Wait  am I understanding you correctly   You re using cin for keyboard input  and you want to stop reading input when the user enters the EOF character   Why would the user ever type in the EOF character   Or did you mean you want to stop reading from a file at the EOF   If you re actually trying to use cin to read an EOF character  then why not just specify the EOF as the delimiter      Needed headers  iostream  char buffer 256   cin get  buffer    x1A       If you mean to stop reading from a file at the EOF  then just use getline and once again specify the EOF as the delimiter      Needed headers  iostream  string  and fstream  string buffer       ifstream fin      fin open  test txt        if fin is open              getline fin buffer   x1A             fin close

User · Answer

After researching KeithB s solution using std  istream iterator  I discovered the std istreambuf iterator   Test program to read all piped input into a string  then write it out again    include  lt iostream gt   include  lt iterator gt   include  lt string gt   int main       std  istreambuf iterator lt char gt  begin std  cin   end    std  string s begin  end     std  cout  lt  lt  s

User · Answer

Wait  am I understanding you correctly   You re using cin for keyboard input  and you want to stop reading input when the user enters the EOF character   Why would the user ever type in the EOF character   Or did you mean you want to stop reading from a file at the EOF   If you re actually trying to use cin to read an EOF character  then why not just specify the EOF as the delimiter      Needed headers  iostream  char buffer 256   cin get  buffer    x1A       If you mean to stop reading from a file at the EOF  then just use getline and once again specify the EOF as the delimiter      Needed headers  iostream  string  and fstream  string buffer       ifstream fin      fin open  test txt        if fin is open              getline fin buffer   x1A             fin close

User · Answer

Probable simplest and generally efficient    include  lt iostream gt  int main         std  cout  lt  lt  std  cin rdbuf        If needed  use stream of other types like std  ostringstream as buffer instead of standard output stream here

User · Answer

You can do it without explicit loops by using stream iterators   I m sure that it uses some kind of loop internally    include  lt string gt   include  lt iostream gt   include  lt istream gt   include  lt ostream gt   include  lt iterator gt   int main        don t skip the whitespace while reading   std  cin  gt  gt  std  noskipws      use stream iterators to copy the stream to a string   std  istream iterator lt char gt  it std  cin     std  istream iterator lt char gt  end    std  string results it  end      std  cout  lt  lt  results

User · Answer

The only way you can read a variable amount of data from stdin is using loops  I ve always found that the std  getline   function works very well   std  string line  while  std  getline std  cin  line         std  cout  lt  lt  line  lt  lt  std  endl      By default getline   reads until a newline  You can specify an alternative termination character  but EOF is not itself a character so you cannot simply make one call to getline

User · Answer

You can do it without explicit loops by using stream iterators   I m sure that it uses some kind of loop internally    include  lt string gt   include  lt iostream gt   include  lt istream gt   include  lt ostream gt   include  lt iterator gt   int main        don t skip the whitespace while reading   std  cin  gt  gt  std  noskipws      use stream iterators to copy the stream to a string   std  istream iterator lt char gt  it std  cin     std  istream iterator lt char gt  end    std  string results it  end      std  cout  lt  lt  results

User · Answer

The only way you can read a variable amount of data from stdin is using loops  I ve always found that the std  getline   function works very well   std  string line  while  std  getline std  cin  line         std  cout  lt  lt  line  lt  lt  std  endl      By default getline   reads until a newline  You can specify an alternative termination character  but EOF is not itself a character so you cannot simply make one call to getline

User · Answer

You can use the std  istream  getline    or preferably the version that works on std  string  function to get an entire line   Both have versions that allow you to specify the delimiter  end of line character    The default for the string version is   n

User · Answer

Using loops    include  lt iostream gt  using namespace std         numbers int n  while  cin  gt  gt  n                lines string line  while  getline cin  line                 characters char c  while  cin get c                resource

User · Answer

You can use the std  istream  getline    or preferably the version that works on std  string  function to get an entire line   Both have versions that allow you to specify the delimiter  end of line character    The default for the string version is   n

User · Answer

One option is to a use a container  e g   std  vector lt char gt  data    and redirect all input into this collection until EOF is received  i e   std  copy std  istream iterator lt char gt  std  cin       std  istream iterator lt char gt         std  back inserter data      However  the used container might need to reallocate memory too often  or you will end with a std  bad alloc exception when your system gets out of memory  In order to solve these problems  you could reserve a fixed amount N of elements and process these amount of elements in isolation  i e   data reserve N       while    some condition is met          std  copy n std  istream iterator lt char gt  std  cin           N          std  back inserter data            process data         data clear

User · Answer

After researching KeithB s solution using std  istream iterator  I discovered the std istreambuf iterator   Test program to read all piped input into a string  then write it out again    include  lt iostream gt   include  lt iterator gt   include  lt string gt   int main       std  istreambuf iterator lt char gt  begin std  cin   end    std  string s begin  end     std  cout  lt  lt  s

User · Answer

You can do it without explicit loops by using stream iterators   I m sure that it uses some kind of loop internally    include  lt string gt   include  lt iostream gt   include  lt istream gt   include  lt ostream gt   include  lt iterator gt   int main        don t skip the whitespace while reading   std  cin  gt  gt  std  noskipws      use stream iterators to copy the stream to a string   std  istream iterator lt char gt  it std  cin     std  istream iterator lt char gt  end    std  string results it  end      std  cout  lt  lt  results

User · Answer

Using loops    include  lt iostream gt  using namespace std         numbers int n  while  cin  gt  gt  n                lines string line  while  getline cin  line                 characters char c  while  cin get c                resource

User · Answer

You can use the std  istream  getline    or preferably the version that works on std  string  function to get an entire line   Both have versions that allow you to specify the delimiter  end of line character    The default for the string version is   n

User · Answer

The only way you can read a variable amount of data from stdin is using loops  I ve always found that the std  getline   function works very well   std  string line  while  std  getline std  cin  line         std  cout  lt  lt  line  lt  lt  std  endl      By default getline   reads until a newline  You can specify an alternative termination character  but EOF is not itself a character so you cannot simply make one call to getline

User · Answer

Sad side note  I decided to use C   IO to be consistent with boost based code  From answers to this question I chose while  std  getline std  cin  line    Using g   version 4 5 3  -O3  in cygwin  mintty  i got 2 MB s throughput  Microsoft Visual C   2010   O2  made it 40 MB s for the same code   After rewriting the IO to pure C while  fgets buf  100  stdin   the throughput jumped to 90 MB s in both tested compilers  That makes a difference for any input bigger than 10 MB

User · Answer

You can do it without explicit loops by using stream iterators   I m sure that it uses some kind of loop internally    include  lt string gt   include  lt iostream gt   include  lt istream gt   include  lt ostream gt   include  lt iterator gt   int main        don t skip the whitespace while reading   std  cin  gt  gt  std  noskipws      use stream iterators to copy the stream to a string   std  istream iterator lt char gt  it std  cin     std  istream iterator lt char gt  end    std  string results it  end      std  cout  lt  lt  results

User · Answer

Sad side note  I decided to use C   IO to be consistent with boost based code  From answers to this question I chose while  std  getline std  cin  line    Using g   version 4 5 3  -O3  in cygwin  mintty  i got 2 MB s throughput  Microsoft Visual C   2010   O2  made it 40 MB s for the same code   After rewriting the IO to pure C while  fgets buf  100  stdin   the throughput jumped to 90 MB s in both tested compilers  That makes a difference for any input bigger than 10 MB

User · Answer

The only way you can read a variable amount of data from stdin is using loops  I ve always found that the std  getline   function works very well   std  string line  while  std  getline std  cin  line         std  cout  lt  lt  line  lt  lt  std  endl      By default getline   reads until a newline  You can specify an alternative termination character  but EOF is not itself a character so you cannot simply make one call to getline

[c++] How to read until EOF from cin in C++

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