What s the best way to check if a file exists in C cross platform

Question

I have read the answers for What s the best way to check if a file exists in C   cross platform   but I m wondering if there is a better way to do this using standard c   libs  Preferably without trying to open the file at all    Both stat and access are pretty much ungoogleable  What should I  include to use these

User · Answer

I would reconsider trying to find out if a file exists   Instead  you should try to open it  in Standard C or C    in the same mode you intend to use it   What use is knowing that the file exists if  say  it isn t writable when you need to use it

User · Answer

Be careful of race conditions  if the file disappears between the  exists  check and the time you open it  your program will fail unexpectedly   It s better to go and open the file  check for failure and if all is good then do something with the file  It s even more important with security-critical code   Details about security and race conditions  http   www ibm com developerworks library l-sprace html

User · Answer

If you are already using the input file stream class  ifstream   you could use its function fail     Example   ifstream myFile   myFile open  file txt        Check for errors if  myFile fail          cerr  lt  lt   Error  File could not be found       exit 1

User · Answer

If you are already using the input file stream class  ifstream   you could use its function fail     Example   ifstream myFile   myFile open  file txt        Check for errors if  myFile fail          cerr  lt  lt   Error  File could not be found       exit 1

User · Answer

I am a happy boost user and would certainly use Andreas  solution   But if you didn t have access to the boost libs you can use the stream library   ifstream file argv 1    if   file           Can t open file     It s not quite as nice as boost  filesystem  exists since the file will actually be opened   but then that s usually the next thing you want to do anyway

User · Answer

How about access    include  lt io h gt   if   access filename  0     -1           File does not exist

User · Answer

NO boost REQUIRED  which would be an overkill     Use stat    not cross platform though as mentioned by pavon   like this    include  lt sys stat h gt   include  lt iostream gt      true if file exists bool fileExists const std  string amp  file        struct stat buf      return  stat file c str     amp buf     0      int main         if  fileExists  test txt              std  cerr  lt  lt   test txt doesn t exist  exiting    n           return -1            return 0      Output   C02QT2UBFVH6-lm   gsamaras  ls test txt ls  test txt  No such file or directory C02QT2UBFVH6-lm   gsamaras  g   -Wall main cpp C02QT2UBFVH6-lm   gsamaras    a out test txt doesn t exist  exiting      Another version  and that  can be found here

User · Answer

If your compiler supports C  17 you don t need boost  you can simply use std  filesystem  exists   include  lt iostream gt     only for std  cout  include  lt filesystem gt   if   std  filesystem  exists  myfile txt          std  cout  lt  lt   File not found    lt  lt  std  endl

User · Answer

Use stat    if it is cross-platform enough for your needs  It is not C   standard though  but POSIX   On MS Windows there is  stat   stat64   stati64   wstat   wstat64   wstati64

User · Answer

NO boost REQUIRED  which would be an overkill     Use stat    not cross platform though as mentioned by pavon   like this    include  lt sys stat h gt   include  lt iostream gt      true if file exists bool fileExists const std  string amp  file        struct stat buf      return  stat file c str     amp buf     0      int main         if  fileExists  test txt              std  cerr  lt  lt   test txt doesn t exist  exiting    n           return -1            return 0      Output   C02QT2UBFVH6-lm   gsamaras  ls test txt ls  test txt  No such file or directory C02QT2UBFVH6-lm   gsamaras  g   -Wall main cpp C02QT2UBFVH6-lm   gsamaras    a out test txt doesn t exist  exiting      Another version  and that  can be found here

User · Answer

How about access    include  lt io h gt   if   access filename  0     -1           File does not exist

User · Answer

I would reconsider trying to find out if a file exists   Instead  you should try to open it  in Standard C or C    in the same mode you intend to use it   What use is knowing that the file exists if  say  it isn t writable when you need to use it

User · Answer

Use stat    if it is cross-platform enough for your needs  It is not C   standard though  but POSIX   On MS Windows there is  stat   stat64   stati64   wstat   wstat64   wstati64

User · Answer

I am a happy boost user and would certainly use Andreas  solution   But if you didn t have access to the boost libs you can use the stream library   ifstream file argv 1    if   file           Can t open file     It s not quite as nice as boost  filesystem  exists since the file will actually be opened   but then that s usually the next thing you want to do anyway

User · Answer

I am a happy boost user and would certainly use Andreas  solution   But if you didn t have access to the boost libs you can use the stream library   ifstream file argv 1    if   file           Can t open file     It s not quite as nice as boost  filesystem  exists since the file will actually be opened   but then that s usually the next thing you want to do anyway

User · Answer

If your compiler supports C  17 you don t need boost  you can simply use std  filesystem  exists   include  lt iostream gt     only for std  cout  include  lt filesystem gt   if   std  filesystem  exists  myfile txt          std  cout  lt  lt   File not found    lt  lt  std  endl

User · Answer

Be careful of race conditions  if the file disappears between the  exists  check and the time you open it  your program will fail unexpectedly   It s better to go and open the file  check for failure and if all is good then do something with the file  It s even more important with security-critical code   Details about security and race conditions  http   www ibm com developerworks library l-sprace html

User · Answer

Use boost  filesystem    include  lt boost filesystem hpp gt   if    boost  filesystem  exists   myfile txt          std  cout  lt  lt   Can t find my file    lt  lt  std  endl

User · Answer

Use boost  filesystem    include  lt boost filesystem hpp gt   if    boost  filesystem  exists   myfile txt          std  cout  lt  lt   Can t find my file    lt  lt  std  endl

User · Answer

Be careful of race conditions  if the file disappears between the  exists  check and the time you open it  your program will fail unexpectedly   It s better to go and open the file  check for failure and if all is good then do something with the file  It s even more important with security-critical code   Details about security and race conditions  http   www ibm com developerworks library l-sprace html

User · Answer

Be careful of race conditions  if the file disappears between the  exists  check and the time you open it  your program will fail unexpectedly   It s better to go and open the file  check for failure and if all is good then do something with the file  It s even more important with security-critical code   Details about security and race conditions  http   www ibm com developerworks library l-sprace html

User · Answer

Use stat    if it is cross-platform enough for your needs  It is not C   standard though  but POSIX   On MS Windows there is  stat   stat64   stati64   wstat   wstat64   wstati64

User · Answer

Use boost  filesystem    include  lt boost filesystem hpp gt   if    boost  filesystem  exists   myfile txt          std  cout  lt  lt   Can t find my file    lt  lt  std  endl

User · Answer

Another possibility consists in using the good   function in the stream    include  lt fstream gt       bool checkExistence const char  filename         ifstream Infield filename        return Infield good

User · Answer

Another possibility consists in using the good   function in the stream    include  lt fstream gt       bool checkExistence const char  filename         ifstream Infield filename        return Infield good

User · Answer

Use boost  filesystem    include  lt boost filesystem hpp gt   if    boost  filesystem  exists   myfile txt          std  cout  lt  lt   Can t find my file    lt  lt  std  endl

User · Answer

I would reconsider trying to find out if a file exists   Instead  you should try to open it  in Standard C or C    in the same mode you intend to use it   What use is knowing that the file exists if  say  it isn t writable when you need to use it

User · Answer

How about access    include  lt io h gt   if   access filename  0     -1           File does not exist

User · Answer

How about access    include  lt io h gt   if   access filename  0     -1           File does not exist

User · Answer

I am a happy boost user and would certainly use Andreas  solution   But if you didn t have access to the boost libs you can use the stream library   ifstream file argv 1    if   file           Can t open file     It s not quite as nice as boost  filesystem  exists since the file will actually be opened   but then that s usually the next thing you want to do anyway

User · Answer

I would reconsider trying to find out if a file exists   Instead  you should try to open it  in Standard C or C    in the same mode you intend to use it   What use is knowing that the file exists if  say  it isn t writable when you need to use it

User · Answer

Use stat    if it is cross-platform enough for your needs  It is not C   standard though  but POSIX   On MS Windows there is  stat   stat64   stati64   wstat   wstat64   wstati64

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