2016-03-09 10:40:25 +00:00
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.\" Copyright 2005, 2012, 2016 Michael Kerrisk <mtk.manpages@gmail.com>
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2016-03-09 03:55:07 +00:00
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.\"
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.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
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.\" Distributed under the GPL.
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.\" %%%LICENSE_END
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.\"
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.\" 2008-12-04, Petr Baudis <pasky@suse.cz>: Document open_wmemstream()
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.\"
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locale.1, localedef.1, _exit.2, accept.2, access.2, acct.2, adjtimex.2, bdflush.2, bind.2, bpf.2, brk.2, chdir.2, chmod.2, chown.2, chroot.2, clock_nanosleep.2, clone.2, close.2, connect.2, copy_file_range.2, create_module.2, delete_module.2, dup.2, epoll_ctl.2, eventfd.2, execve.2, fallocate.2, fanotify_init.2, fcntl.2, flock.2, fork.2, fsync.2, futex.2, get_kernel_syms.2, getdomainname.2, getgroups.2, gethostname.2, getpagesize.2, getpeername.2, getsid.2, getsockname.2, getsockopt.2, gettimeofday.2, init_module.2, ioctl.2, ioctl_list.2, ioperm.2, iopl.2, kexec_load.2, kill.2, killpg.2, link.2, listen.2, llseek.2, lseek.2, madvise.2, memfd_create.2, mincore.2, mkdir.2, mknod.2, mmap.2, mount.2, nanosleep.2, nice.2, open.2, personality.2, pipe.2, poll.2, posix_fadvise.2, read.2, readahead.2, readlink.2, readv.2, recv.2, recvmmsg.2, rename.2, request_key.2, sched_setaffinity.2, sched_setattr.2, select.2, select_tut.2, semctl.2, semop.2, send.2, sendfile.2, sendmmsg.2, seteuid.2, setns.2, setpgid.2, setreuid.2, shutdown.2, sigaction.2, sigaltstack.2, signal.2, signalfd.2, sigpending.2, sigprocmask.2, sigsuspend.2, socketpair.2, splice.2, stat.2, statfs.2, stime.2, symlink.2, sync.2, syscall.2, syscalls.2, times.2, truncate.2, unlink.2, unshare.2, uselib.2, utimensat.2, vfork.2, vhangup.2, wait.2, wait4.2, write.2, a64l.3, abs.3, acos.3, acosh.3, addseverity.3, adjtime.3, aio_read.3, aio_write.3, asin.3, asinh.3, atan.3, atan2.3, atanh.3, atoi.3, backtrace.3, cbrt.3, ceil.3, cfree.3, clearenv.3, clock_getcpuclockid.3, clog10.3, cmsg.3, copysign.3, cos.3, cosh.3, ctermid.3, ctime.3, daemon.3, dirfd.3, div.3, dl_iterate_phdr.3, drand48.3, drand48_r.3, dysize.3, ecvt.3, ecvt_r.3, endian.3, erf.3, erfc.3, errno.3, exec.3, exp.3, exp2.3, expm1.3, fabs.3, fdim.3, ferror.3, fexecve.3, ffs.3, fgetgrent.3, fgetpwent.3, finite.3, flockfile.3, floor.3, fma.3, fmax.3, fmin.3, fmod.3, fopen.3, fpclassify.3, frexp.3, fseeko.3, fts.3, futimes.3, fwide.3, gamma.3, gcvt.3, getaddrinfo.3, getcwd.3, getdate.3, getdirentries.3, getdtablesize.3, getgrent.3, getgrent_r.3, getgrnam.3, getgrouplist.3, gethostbyname.3, gethostid.3, getline.3, getloadavg.3, getmntent.3, getnameinfo.3, getnetent_r.3, getpass.3, getprotoent_r.3, getpwent.3, getpwent_r.3, getpwnam.3, getrpcent_r.3, getservent_r.3, getspnam.3, getsubopt.3, getusershell.3, getutent.3, getw.3, gsignal.3, hypot.3, ilogb.3, inet.3, initgroups.3, insque.3, isalpha.3, isgreater.3, iswblank.3, j0.3, ldexp.3, lgamma.3, lio_listio.3, lockf.3, log.3, log10.3, log1p.3, log2.3, logb.3, lrint.3, lround.3, makedev.3, matherr.3, mbsnrtowcs.3, mkdtemp.3, mkfifo.3, mkstemp.3, mktemp.3, modf.3, mq_close.3, mq_getattr.3, mq_notify.3, mq_receive.3, mq_send.3, nan.3, nextafter.3, on_exit.3, open_memstream.3, opendir.3, perror.3, popen.3, posix_fallocate.3, posix_madvise.3, posix_memalign.3, posix_openpt.3, posix_spawn.3, pow.3, printf.3, profil.3, psignal.3, pthread_attr_setstack.3, pthread_setaffinity_np.3, putenv.3, putpwent.3, qecvt.3, rand.3, random.3, random_r.3, rcmd.3, readdir.3, realpath.3, remainder.3, remquo.3, rexec.3, rint.3, round.3, rpc.3, rpmatch.3, scalb.3, scalbln.3, scandir.3, scanf.3, seekdir.3, sem_wait.3, setbuf.3, setenv.3, setjmp.3, setnetgrent.3, siginterrupt.3, signbit.3, significand.3, sigset.3, sigsetops.3, sigvec.3, sigwait.3, sin.3, sinh.3, sleep.3, sockatmark.3, sqrt.3, statvfs.3, stpcpy.3, stpncpy.3, strdup.3, strerror.3, strftime.3, strlen.3, strnlen.3, strsep.3, strsignal.3, strtod.3, strtok.3, strtol.3, strtoul.3, syslog.3, system.3, tan.3, tanh.3, telldir.3, tempnam.3, termios.3, tgamma.3, timegm.3, timeradd.3, tmpfile.3, tmpnam.3, toascii.3, trunc.3, ttyslot.3, tzset.3, ualarm.3, unlocked_stdio.3, usleep.3, wcpcpy.3, wcpncpy.3, wcscasecmp.3, wcsdup.3, wcsncasecmp.3, wcsnlen.3, wcsnrtombs.3, wprintf.3, y0.3, pts.4, st.4, tty_ioctl.4, elf.5, gai.conf.5, group.5, locale.5, nsswitch.conf.5, proc.5, utmp.5, aio.7, capabilities.7, credentials.7, environ.7, epoll.7, fanotify.7, feature_test_macros.7, inotify.7, ip.7, mq_overview.7, namespaces.7, pipe.7, signal.7, socket.7, standards.7, svipc.7, symlink.7, time.7, unicode.7, unix.7: tstamp
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2016-03-15 03:46:01 +00:00
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.TH OPEN_MEMSTREAM 3 2016-03-15 "GNU" "Linux Programmer's Manual"
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2016-03-09 03:55:07 +00:00
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.SH NAME
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open_memstream, open_wmemstream \- open a dynamic memory buffer stream
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.SH SYNOPSIS
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.nf
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.B #include <stdio.h>
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.BI "FILE *open_memstream(char **" ptr ", size_t *" sizeloc );
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.B #include <wchar.h>
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.BI "FILE *open_wmemstream(wchar_t **" ptr ", size_t *" sizeloc );
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.fi
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR open_memstream (),
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.BR open_wmemstream ():
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.PD 0
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.ad l
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.RS 4
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.TP 4
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Since glibc 2.10:
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_POSIX_C_SOURCE\ >=\ 200809L
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.TP
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Before glibc 2.10:
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_GNU_SOURCE
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.RE
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.ad
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.PD
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.SH DESCRIPTION
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The
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.BR open_memstream ()
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2016-03-10 01:51:53 +00:00
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function opens a stream for writing to a memory buffer.
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The function dynamically allocates the buffer,
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and the buffer automatically grows as needed.
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2016-03-09 04:10:01 +00:00
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Initially, the buffer has a size of zero.
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2016-03-09 03:55:07 +00:00
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After closing the stream, the caller should
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.BR free (3)
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this buffer.
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The locations pointed to by
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.IR ptr
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and
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.I sizeloc
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2016-03-10 01:51:53 +00:00
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are used to report, respectively,
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the current location and the size of the buffer.
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The locations referred to by these pointers are updated
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each time the stream is flushed
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.RB ( fflush (3))
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and when the stream is closed
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.RB ( fclose (3)).
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2016-03-09 03:55:07 +00:00
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These values remain valid only as long as the caller
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performs no further output on the stream.
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If further output is performed, then the stream
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2016-03-10 01:51:53 +00:00
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must again be flushed before trying to access these values.
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2016-03-09 03:55:07 +00:00
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A null byte is maintained at the end of the buffer.
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This byte is
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.I not
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included in the size value stored at
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.IR sizeloc .
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2016-03-09 04:09:37 +00:00
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The stream maintains the notion of a current position,
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which is initially zero (the start of the buffer).
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Each write operation implicitly adjusts the buffer position.
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The stream's buffer position can be explicitly changed with
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2016-03-09 03:55:07 +00:00
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.BR fseek (3)
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or
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.BR fseeko (3).
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Moving the buffer position past the end
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of the data already written fills the intervening space with
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2016-03-10 01:51:53 +00:00
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null characters.
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2016-03-09 03:55:07 +00:00
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The
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.BR open_wmemstream ()
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is similar to
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.BR open_memstream (),
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but operates on wide characters instead of bytes.
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.SH RETURN VALUE
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Upon successful completion,
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.BR open_memstream ()
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and
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.BR open_wmemstream ()
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return a
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.I FILE
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pointer.
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Otherwise, NULL is returned and
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.I errno
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is set to indicate the error.
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.SH VERSIONS
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.BR open_memstream ()
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was already available in glibc 1.0.x.
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.BR open_wmemstream ()
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is available since glibc 2.4.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lb lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR open_memstream (),
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.br
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.BR open_wmemstream
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T} Thread safety MT-Safe
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.TE
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.SH CONFORMING TO
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POSIX.1-2008.
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These functions are not specified in POSIX.1-2001,
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and are not widely available on other systems.
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.SH NOTES
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There is no file descriptor associated with the file stream
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returned by these functions
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(i.e.,
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.BR fileno (3)
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will return an error if called on the returned stream).
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.SH BUGS
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In glibc before version 2.7, seeking past the end of a stream created by
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.BR open_memstream ()
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does not enlarge the buffer; instead the
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.BR fseek (3)
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call fails, returning \-1.
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.\" http://sourceware.org/bugzilla/show_bug.cgi?id=1996
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.SH EXAMPLE
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See
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.BR fmemopen (3).
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.SH SEE ALSO
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.BR fmemopen (3),
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2016-03-10 01:52:22 +00:00
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.BR fopen (3),
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.BR setbuf (3)
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