xref: /petsc/src/sys/fileio/mprint.c (revision 0b8bdde92eb4bc9ed9cee42fe7fcadba66103007)

/*
      Utilities routines to add simple ASCII IO capability.
*/
#include <../src/sys/fileio/mprint.h>
#include <errno.h>
/*
   If petsc_history is on, then all Petsc*Printf() results are saved
   if the appropriate (usually .petschistory) file.
*/
PETSC_INTERN FILE *petsc_history;
/*
     Allows one to overwrite where standard out is sent. For example
     PETSC_STDOUT = fopen("/dev/ttyXX","w") will cause all standard out
     writes to go to terminal XX; assuming you have write permission there
*/
FILE *PETSC_STDOUT = NULL;
/*
     Allows one to overwrite where standard error is sent. For example
     PETSC_STDERR = fopen("/dev/ttyXX","w") will cause all standard error
     writes to go to terminal XX; assuming you have write permission there
*/
FILE *PETSC_STDERR = NULL;

/*@C
  PetscFormatConvertGetSize - Gets the length of a string needed to hold data converted with `PetscFormatConvert()` based on the format

  No Fortran Support

  Input Parameter:
. format - the PETSc format string

  Output Parameter:
. size - the needed length of the new format

  Level: developer

.seealso: `PetscFormatConvert()`, `PetscVSNPrintf()`, `PetscVFPrintf()`
@*/
PetscErrorCode PetscFormatConvertGetSize(const char format[], size_t *size)
{
  size_t   sz = 0;
  PetscInt i  = 0;

  PetscFunctionBegin;
  PetscAssertPointer(format, 1);
  PetscAssertPointer(size, 2);
  while (format[i]) {
    if (format[i] == '%') {
      if (format[i + 1] == '%') {
        i += 2;
        sz += 2;
        continue;
      }
      /* Find the letter */
      while (format[i] && (format[i] <= '9')) {
        ++i;
        ++sz;
      }
      switch (format[i]) {
#if PetscDefined(USE_64BIT_INDICES)
      case 'D':
        sz += 2;
        break;
#endif
      case 'g':
        sz += 4;
      default:
        break;
      }
    }
    ++i;
    ++sz;
  }
  *size = sz + 1; /* space for NULL character */
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscFormatConvert - converts %g to [|%g|] so that `PetscVSNPrintf()` can ensure all %g formatted numbers have a decimal point when printed.

  No Fortran Support

  Input Parameter:
. format - the PETSc format string

  Output Parameter:
. newformat - the formatted string, must be long enough to hold result

  Level: developer

  Note:
  The decimal point is then used by the `petscdiff` script so that differences in floating
  point number output is ignored in the test harness.

  Deprecated usage also converts the `%D` to `%d` for 32-bit PETSc indices and to `%lld` for
  64-bit PETSc indices. This feature is no longer used in PETSc code instead use %"
  PetscInt_FMT " in the format string.

.seealso: `PetscFormatConvertGetSize()`, `PetscVSNPrintf()`, `PetscVFPrintf()`
@*/
PetscErrorCode PetscFormatConvert(const char format[], char newformat[])
{
  PetscInt i = 0, j = 0;

  PetscFunctionBegin;
  while (format[i]) {
    if (format[i] == '%' && format[i + 1] == '%') {
      newformat[j++] = format[i++];
      newformat[j++] = format[i++];
    } else if (format[i] == '%') {
      if (format[i + 1] == 'g') {
        newformat[j++] = '[';
        newformat[j++] = '|';
      }
      /* Find the letter */
      for (; format[i] && format[i] <= '9'; i++) newformat[j++] = format[i];
      switch (format[i]) {
      case 'D':
#if !defined(PETSC_USE_64BIT_INDICES)
        newformat[j++] = 'd';
#else
        newformat[j++] = 'l';
        newformat[j++] = 'l';
        newformat[j++] = 'd';
#endif
        break;
      case 'g':
        newformat[j++] = format[i];
        if (format[i - 1] == '%') {
          newformat[j++] = '|';
          newformat[j++] = ']';
        }
        break;
      case 'G':
        SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "%%G format is no longer supported, use %%g and cast the argument to double");
      case 'F':
        SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "%%F format is no longer supported, use %%f and cast the argument to double");
      default:
        newformat[j++] = format[i];
        break;
      }
      i++;
    } else newformat[j++] = format[i++];
  }
  newformat[j] = 0;
  PetscFunctionReturn(PETSC_SUCCESS);
}

#define PETSCDEFAULTBUFFERSIZE 8 * 1024

/*@C
  PetscVSNPrintf - The PETSc version of `vsnprintf()`. Ensures that all `%g` formatted arguments' output contains the decimal point (which is used by the test harness)

  No Fortran Support

  Input Parameters:
+ str    - location to put result
. len    - the length of `str`
. format - the PETSc format string
- Argp   - the variable argument list to format

  Output Parameter:
. fullLength - the amount of space in `str` actually used.

  Level: developer

  Developer Notes:
  This function may be called from an error handler, if an error occurs when it is called by the error handler than likely
  a recursion will occur resulting in a crash of the program.

  If the length of the format string `format` is on the order of `PETSCDEFAULTBUFFERSIZE` (8 * 1024 bytes) or larger, this function will call `PetscMalloc()`

.seealso: `PetscFormatConvert()`, `PetscFormatConvertGetSize()`, `PetscErrorPrintf()`, `PetscVPrintf()`
@*/
PetscErrorCode PetscVSNPrintf(char str[], size_t len, const char format[], size_t *fullLength, va_list Argp)
{
  char  *newformat = NULL;
  char   formatbuf[PETSCDEFAULTBUFFERSIZE];
  size_t newLength;
  int    flen;

  PetscFunctionBegin;
  PetscCall(PetscFormatConvertGetSize(format, &newLength));
  if (newLength < sizeof(formatbuf)) {
    newformat = formatbuf;
    newLength = sizeof(formatbuf) - 1;
  } else {
    PetscCall(PetscMalloc1(newLength, &newformat));
  }
  PetscCall(PetscFormatConvert(format, newformat));
#if defined(PETSC_HAVE_VSNPRINTF)
  flen = vsnprintf(str, len, newformat, Argp);
#else
  #error "vsnprintf not found"
#endif
  if (newLength > sizeof(formatbuf) - 1) PetscCall(PetscFree(newformat));
  {
    PetscBool foundedot;
    size_t    cnt = 0, ncnt = 0, leng;
    PetscCall(PetscStrlen(str, &leng));
    if (leng > 4) {
      for (cnt = 0; cnt < leng - 4; cnt++) {
        if (str[cnt] == '[' && str[cnt + 1] == '|') {
          flen -= 4;
          cnt++;
          cnt++;
          foundedot = PETSC_FALSE;
          for (; cnt < leng - 1; cnt++) {
            if (str[cnt] == '|' && str[cnt + 1] == ']') {
              cnt++;
              if (!foundedot) str[ncnt++] = '.';
              ncnt--;
              break;
            } else {
              if (str[cnt] == 'e' || str[cnt] == '.') foundedot = PETSC_TRUE;
              str[ncnt++] = str[cnt];
            }
          }
        } else {
          str[ncnt] = str[cnt];
        }
        ncnt++;
      }
      while (cnt < leng) {
        str[ncnt] = str[cnt];
        ncnt++;
        cnt++;
      }
      str[ncnt] = 0;
    }
  }
  if (fullLength) *fullLength = 1 + (size_t)flen;
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscFFlush - Flush a file stream

  Input Parameter:
. fd - The file stream handle

  Level: intermediate

  Notes:
  For output streams (and for update streams on which the last operation was output), writes
  any unwritten data from the stream's buffer to the associated output device.

  For input streams (and for update streams on which the last operation was input), the
  behavior is undefined.

  If `fd` is `NULL`, all open output streams are flushed, including ones not directly
  accessible to the program.

  Fortran Note:
  Use `PetscFlush()`

.seealso: `PetscPrintf()`, `PetscFPrintf()`, `PetscVFPrintf()`, `PetscVSNPrintf()`
@*/
PetscErrorCode PetscFFlush(FILE *fd)
{
  int err;

  PetscFunctionBegin;
  if (fd) PetscAssertPointer(fd, 1);
  err = fflush(fd);
#if !defined(PETSC_MISSING_SIGPIPE) && defined(EPIPE) && defined(ECONNRESET)
  if (fd && err && (errno == EPIPE || errno == ECONNRESET)) err = 0; /* ignore error, rely on SIGPIPE */
#endif
  // could also use PetscCallExternal() here, but since we can get additional error explanation
  // from strerror() we opted for a manual check
  PetscCheck(0 == err, PETSC_COMM_SELF, PETSC_ERR_FILE_WRITE, "Error in fflush() due to \"%s\"", strerror(errno));
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscVFPrintfDefault -  All PETSc standard out and error messages are sent through this function; so, in theory, this can
  can be replaced with something that does not simply write to a file.

  No Fortran Support

  Input Parameters:
+ fd     - the file descriptor to write to
. format - the format string to write with
- Argp   - the variable argument list of items to format and write

  Level: developer

  Note:
  For error messages this may be called by any MPI process, for regular standard out it is
  called only by MPI rank 0 of a given communicator

  Example Usage:
  To use, write your own function for example,
.vb
   PetscErrorCode mypetscvfprintf(FILE *fd, const char format[], va_list Argp)
   {

     PetscFunctionBegin;
      if (fd != stdout && fd != stderr) {  handle regular files
         CHKERR(PetscVFPrintfDefault(fd,format,Argp));
     } else {
        char   buff[BIG];
        size_t length;
        PetscCall(PetscVSNPrintf(buff,BIG,format,&length,Argp));
        now send buff to whatever stream or whatever you want
    }
    PetscFunctionReturn(PETSC_SUCCESS);
   }
.ve
  then before the call to `PetscInitialize()` do the assignment `PetscVFPrintf = mypetscvfprintf`;

  Developer Notes:
  This could be called by an error handler, if that happens then a recursion of the error handler may occur
  and a resulting crash

.seealso: `PetscVSNPrintf()`, `PetscErrorPrintf()`, `PetscFFlush()`
@*/
PetscErrorCode PetscVFPrintfDefault(FILE *fd, const char format[], va_list Argp)
{
  char   str[PETSCDEFAULTBUFFERSIZE];
  char  *buff = str;
  size_t fullLength;
#if defined(PETSC_HAVE_VA_COPY)
  va_list Argpcopy;
#endif

  PetscFunctionBegin;
#if defined(PETSC_HAVE_VA_COPY)
  va_copy(Argpcopy, Argp);
#endif
  PetscCall(PetscVSNPrintf(str, sizeof(str), format, &fullLength, Argp));
  if (fullLength > sizeof(str)) {
    PetscCall(PetscMalloc1(fullLength, &buff));
#if defined(PETSC_HAVE_VA_COPY)
    PetscCall(PetscVSNPrintf(buff, fullLength, format, NULL, Argpcopy));
#else
    SETERRQ(PETSC_COMM_SELF, PETSC_ERR_LIB, "C89 does not support va_copy() hence cannot print long strings with PETSc printing routines");
#endif
  }
#if defined(PETSC_HAVE_VA_COPY)
  va_end(Argpcopy);
#endif
  {
    int err;

    // POSIX C sets errno but otherwise it may not be set for *printf() system calls
    // https://pubs.opengroup.org/onlinepubs/9699919799/functions/fprintf.html
    errno = 0;
    err   = fprintf(fd, "%s", buff);
    // cannot use PetscCallExternal() for fprintf since the return value is "number of
    // characters transmitted to the output stream" on success
    PetscCheck(err >= 0, PETSC_COMM_SELF, PETSC_ERR_FILE_WRITE, "fprintf() returned error code %d: %s", err, errno > 0 ? strerror(errno) : "unknown (errno not set)");
  }
  PetscCall(PetscFFlush(fd));
  if (buff != str) PetscCall(PetscFree(buff));
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscSNPrintf - Prints to a string of given length

  Not Collective, No Fortran Support

  Input Parameters:
+ len    - the length of `str`
- format - the usual `printf()` format string

  Output Parameter:
. str - the resulting string

  Level: intermediate

.seealso: `PetscSynchronizedFlush()`, `PetscSynchronizedFPrintf()`, `PetscFPrintf()`, `PetscVSNPrintf()`,
          `PetscPrintf()`, `PetscViewerASCIIPrintf()`, `PetscViewerASCIISynchronizedPrintf()`,
          `PetscVFPrintf()`, `PetscFFlush()`
@*/
PetscErrorCode PetscSNPrintf(char str[], size_t len, const char format[], ...)
{
  size_t  fullLength;
  va_list Argp;

  PetscFunctionBegin;
  va_start(Argp, format);
  PetscCall(PetscVSNPrintf(str, len, format, &fullLength, Argp));
  va_end(Argp);
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscSNPrintfCount - Prints to a string of given length, returns count of characters printed

  Not Collective, No Fortran Support

  Input Parameters:
+ len    - the length of `str`
. format - the usual `printf()` format string
- ...    - args to format

  Output Parameters:
+ str       - the resulting string
- countused - number of characters printed

  Level: intermediate

.seealso: `PetscSynchronizedFlush()`, `PetscSynchronizedFPrintf()`, `PetscFPrintf()`, `PetscVSNPrintf()`,
          `PetscPrintf()`, `PetscViewerASCIIPrintf()`, `PetscViewerASCIISynchronizedPrintf()`, `PetscSNPrintf()`, `PetscVFPrintf()`
@*/
PetscErrorCode PetscSNPrintfCount(char str[], size_t len, const char format[], size_t *countused, ...)
{
  va_list Argp;

  PetscFunctionBegin;
  va_start(Argp, countused);
  PetscCall(PetscVSNPrintf(str, len, format, countused, Argp));
  va_end(Argp);
  PetscFunctionReturn(PETSC_SUCCESS);
}

PrintfQueue petsc_printfqueue = NULL, petsc_printfqueuebase = NULL;
int         petsc_printfqueuelength = 0;

static inline PetscErrorCode PetscVFPrintf_Private(FILE *fd, const char format[], va_list Argp)
{
  const PetscBool tee = (PetscBool)(petsc_history && (fd != petsc_history));
  va_list         cpy;

  PetscFunctionBegin;
  // must do this before we possibly consume Argp
  if (tee) va_copy(cpy, Argp);
  PetscCall((*PetscVFPrintf)(fd, format, Argp));
  if (tee) {
    PetscCall((*PetscVFPrintf)(petsc_history, format, cpy));
    va_end(cpy);
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

PETSC_INTERN PetscErrorCode PetscVFPrintf_Internal(FILE *fd, const char format[], ...)
{
  va_list Argp;

  PetscFunctionBegin;
  va_start(Argp, format);
  PetscCall(PetscVFPrintf_Private(fd, format, Argp));
  va_end(Argp);
  PetscFunctionReturn(PETSC_SUCCESS);
}

static inline PetscErrorCode PetscSynchronizedFPrintf_Private(MPI_Comm comm, FILE *fp, const char format[], va_list Argp)
{
  PetscMPIInt rank;
  va_list     cpy;

  PetscFunctionBegin;
  PetscCallMPI(MPI_Comm_rank(comm, &rank));
  /* First processor prints immediately to fp */
  if (rank == 0) {
    va_copy(cpy, Argp);
    PetscCall(PetscVFPrintf_Private(fp, format, cpy));
    va_end(cpy);
  } else { /* other processors add to local queue */
    PrintfQueue next;
    size_t      fullLength = PETSCDEFAULTBUFFERSIZE;

    PetscCall(PetscNew(&next));
    if (petsc_printfqueue) {
      petsc_printfqueue->next = next;
      petsc_printfqueue       = next;
      petsc_printfqueue->next = NULL;
    } else petsc_printfqueuebase = petsc_printfqueue = next;
    petsc_printfqueuelength++;
    next->size   = 0;
    next->string = NULL;
    while (fullLength >= next->size) {
      next->size = fullLength + 1;
      PetscCall(PetscFree(next->string));
      PetscCall(PetscMalloc1(next->size, &next->string));
      PetscCall(PetscArrayzero(next->string, next->size));
      va_copy(cpy, Argp);
      PetscCall(PetscVSNPrintf(next->string, next->size, format, &fullLength, cpy));
      va_end(cpy);
    }
  }
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscSynchronizedPrintf - Prints synchronized output from multiple MPI processes.
  Output of the first processor is followed by that of the second, etc.

  Not Collective

  Input Parameters:
+ comm   - the MPI communicator
- format - the usual `printf()` format string

  Level: intermediate

  Note:
  REQUIRES a call to `PetscSynchronizedFlush()` by all the processes after the completion of the calls to `PetscSynchronizedPrintf()` for the information
  from all the processors to be printed.

  Fortran Note:
  The call sequence is `PetscSynchronizedPrintf`(`MPI_Comm`, `character`(*), `PetscErrorCode` ierr).
  That is, you can only pass a single character string from Fortran.

.seealso: `PetscSynchronizedFlush()`, `PetscSynchronizedFPrintf()`, `PetscFPrintf()`,
          `PetscPrintf()`, `PetscViewerASCIIPrintf()`, `PetscViewerASCIISynchronizedPrintf()`,
          `PetscFFlush()`
@*/
PetscErrorCode PetscSynchronizedPrintf(MPI_Comm comm, const char format[], ...)
{
  va_list Argp;

  PetscFunctionBegin;
  va_start(Argp, format);
  PetscCall(PetscSynchronizedFPrintf_Private(comm, PETSC_STDOUT, format, Argp));
  va_end(Argp);
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscSynchronizedFPrintf - Prints synchronized output to the specified file from
  several MPI processes.  Output of the first process is followed by that of the
  second, etc.

  Not Collective

  Input Parameters:
+ comm   - the MPI communicator
. fp     - the file pointer, `PETSC_STDOUT` or value obtained from `PetscFOpen()`
- format - the usual `printf()` format string

  Level: intermediate

  Note:
  REQUIRES a intervening call to `PetscSynchronizedFlush()` for the information
  from all the processors to be printed.

  Fortran Note:
  The call sequence is `PetscSynchronizedPrintf`(`MPI_Comm`, fp, `character`(*), `PetscErrorCode` ierr).
  That is, you can only pass a single character string from Fortran.

.seealso: `PetscSynchronizedPrintf()`, `PetscSynchronizedFlush()`, `PetscFPrintf()`,
          `PetscFOpen()`, `PetscViewerASCIISynchronizedPrintf()`, `PetscViewerASCIIPrintf()`,
          `PetscFFlush()`
@*/
PetscErrorCode PetscSynchronizedFPrintf(MPI_Comm comm, FILE *fp, const char format[], ...)
{
  va_list Argp;

  PetscFunctionBegin;
  va_start(Argp, format);
  PetscCall(PetscSynchronizedFPrintf_Private(comm, fp, format, Argp));
  va_end(Argp);
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscSynchronizedFlush - Flushes to the screen output from all processors
  involved in previous `PetscSynchronizedPrintf()`/`PetscSynchronizedFPrintf()` calls.

  Collective

  Input Parameters:
+ comm - the MPI communicator
- fd   - the file pointer (valid on MPI rank 0 of the communicator), `PETSC_STDOUT` or value obtained from `PetscFOpen()`

  Level: intermediate

  Note:
  If `PetscSynchronizedPrintf()` and/or `PetscSynchronizedFPrintf()` are called with
  different MPI communicators there must be an intervening call to `PetscSynchronizedFlush()` between the calls with different MPI communicators.

.seealso: `PetscSynchronizedPrintf()`, `PetscFPrintf()`, `PetscPrintf()`, `PetscViewerASCIIPrintf()`,
          `PetscViewerASCIISynchronizedPrintf()`
@*/
PetscErrorCode PetscSynchronizedFlush(MPI_Comm comm, FILE *fd)
{
  PetscMPIInt rank, size, tag, i, j, n = 0, dummy = 0;
  char       *message;
  MPI_Status  status;

  PetscFunctionBegin;
  PetscCall(PetscCommDuplicate(comm, &comm, &tag));
  PetscCallMPI(MPI_Comm_rank(comm, &rank));
  PetscCallMPI(MPI_Comm_size(comm, &size));

  /* First processor waits for messages from all other processors */
  if (rank == 0) {
    if (!fd) fd = PETSC_STDOUT;
    for (i = 1; i < size; i++) {
      /* to prevent a flood of messages to process zero, request each message separately */
      PetscCallMPI(MPI_Send(&dummy, 1, MPI_INT, i, tag, comm));
      PetscCallMPI(MPI_Recv(&n, 1, MPI_INT, i, tag, comm, &status));
      for (j = 0; j < n; j++) {
        PetscMPIInt size = 0;

        PetscCallMPI(MPI_Recv(&size, 1, MPI_INT, i, tag, comm, &status));
        PetscCall(PetscMalloc1(size, &message));
        PetscCallMPI(MPI_Recv(message, size, MPI_CHAR, i, tag, comm, &status));
        PetscCall(PetscFPrintf(comm, fd, "%s", message));
        PetscCall(PetscFree(message));
      }
    }
  } else { /* other processors send queue to processor 0 */
    PrintfQueue next = petsc_printfqueuebase, previous;

    PetscCallMPI(MPI_Recv(&dummy, 1, MPI_INT, 0, tag, comm, &status));
    PetscCallMPI(MPI_Send(&petsc_printfqueuelength, 1, MPI_INT, 0, tag, comm));
    for (i = 0; i < petsc_printfqueuelength; i++) {
      PetscCallMPI(MPI_Send(&next->size, 1, MPI_INT, 0, tag, comm));
      PetscCallMPI(MPI_Send(next->string, (PetscMPIInt)next->size, MPI_CHAR, 0, tag, comm));
      previous = next;
      next     = next->next;
      PetscCall(PetscFree(previous->string));
      PetscCall(PetscFree(previous));
    }
    petsc_printfqueue       = NULL;
    petsc_printfqueuelength = 0;
  }
  PetscCall(PetscCommDestroy(&comm));
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscFPrintf - Prints to a file, only from the first
  MPI process in the communicator.

  Not Collective

  Input Parameters:
+ comm   - the MPI communicator
. fd     - the file pointer, `PETSC_STDOUT` or value obtained from `PetscFOpen()`
- format - the usual `printf()` format string

  Level: intermediate

  Fortran Note:
  The call sequence is `PetscFPrintf`(`MPI_Comm`, fp, `character`(*), `PetscErrorCode` ierr).
  That is, you can only pass a single character string from Fortran.

  Developer Notes:
  This maybe, and is, called from PETSc error handlers and `PetscMallocValidate()` hence it does not use `PetscCallMPI()` which
  could recursively restart the malloc validation.

.seealso: `PetscPrintf()`, `PetscSynchronizedPrintf()`, `PetscViewerASCIIPrintf()`,
          `PetscViewerASCIISynchronizedPrintf()`, `PetscSynchronizedFlush()`, `PetscFFlush()`
@*/
PetscErrorCode PetscFPrintf(MPI_Comm comm, FILE *fd, const char format[], ...)
{
  PetscMPIInt rank;
  va_list     Argp;

  PetscFunctionBegin;
  PetscCallMPI(MPI_Comm_rank(comm, &rank));
  if (PetscLikely(rank != 0)) PetscFunctionReturn(PETSC_SUCCESS);
  va_start(Argp, format);
  PetscCall(PetscVFPrintf_Private(fd, format, Argp));
  va_end(Argp);
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscPrintf - Prints to standard out, only from the first
  MPI process in the communicator. Calls from other processes are ignored.

  Not Collective

  Input Parameters:
+ comm   - the communicator
- format - the usual `printf()` format string

  Level: intermediate

  Note:
  Deprecated information: `PetscPrintf()` supports some format specifiers that are unique to PETSc.
  See the manual page for `PetscFormatConvert()` for details.

  Fortran Notes:
  The call sequence is `PetscPrintf`(`MPI_Comm`, `character(*)`, `PetscErrorCode` ierr).
  That is, you can only pass a single character string from Fortran.

.seealso: `PetscFPrintf()`, `PetscSynchronizedPrintf()`, `PetscFormatConvert()`, `PetscFFlush()`
@*/
PetscErrorCode PetscPrintf(MPI_Comm comm, const char format[], ...)
{
  PetscMPIInt rank;
  va_list     Argp;

  PetscFunctionBegin;
  PetscCallMPI(MPI_Comm_rank(comm, &rank));
  if (PetscLikely(rank != 0)) PetscFunctionReturn(PETSC_SUCCESS);
  va_start(Argp, format);
  PetscCall(PetscVFPrintf_Private(PETSC_STDOUT, format, Argp));
  va_end(Argp);
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscHelpPrintfDefault(MPI_Comm comm, const char format[], ...)
{
  PetscMPIInt rank;
  va_list     Argp;

  PetscFunctionBegin;
  PetscCallMPI(MPI_Comm_rank(comm, &rank));
  if (PetscLikely(rank != 0)) PetscFunctionReturn(PETSC_SUCCESS);
  va_start(Argp, format);
  PetscCall(PetscVFPrintf_Private(PETSC_STDOUT, format, Argp));
  va_end(Argp);
  PetscFunctionReturn(PETSC_SUCCESS);
}

/*@C
  PetscSynchronizedFGets - Multiple MPI processes all get the same line from a file.

  Collective

  Input Parameters:
+ comm - the MPI communicator
. fp   - the file pointer
- len  - the length of `string`

  Output Parameter:
. string - the line read from the file, at end of file `string`[0] == 0

  Level: intermediate

.seealso: `PetscSynchronizedPrintf()`, `PetscSynchronizedFlush()`,
          `PetscFOpen()`, `PetscViewerASCIISynchronizedPrintf()`, `PetscViewerASCIIPrintf()`
@*/
PetscErrorCode PetscSynchronizedFGets(MPI_Comm comm, FILE *fp, size_t len, char string[])
{
  PetscMPIInt rank;

  PetscFunctionBegin;
  PetscCallMPI(MPI_Comm_rank(comm, &rank));
  if (rank == 0) {
    if (!fgets(string, (int)len, fp)) {
      string[0] = 0;
      PetscCheck(feof(fp), PETSC_COMM_SELF, PETSC_ERR_FILE_READ, "Error reading from file due to \"%s\"", strerror(errno));
    }
  }
  PetscCallMPI(MPI_Bcast(string, (PetscMPIInt)len, MPI_BYTE, 0, comm));
  PetscFunctionReturn(PETSC_SUCCESS);
}

PetscErrorCode PetscFormatRealArray(char buf[], size_t len, const char *fmt, PetscInt n, const PetscReal x[])
{
  PetscInt i;
  size_t   left, count;
  char    *p;

  PetscFunctionBegin;
  for (i = 0, p = buf, left = len; i < n; i++) {
    PetscCall(PetscSNPrintfCount(p, left, fmt, &count, (double)x[i]));
    PetscCheck(count < left, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Insufficient space in buffer");
    left -= count;
    p += count - 1;
    *p++ = ' ';
  }
  p[i ? 0 : -1] = 0;
  PetscFunctionReturn(PETSC_SUCCESS);
}