Document pread() and pwrite().
Obtained from: NetBSD (mostly)
This commit is contained in:
Dmitrij Tejblum
parent
6f749ef4fc
commit
88874fcfe6
lib/libc/sys
@ -1,5 +1,5 @@
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# @(#)Makefile.inc 8.3 (Berkeley) 10/24/94
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# $Id: Makefile.inc,v 1.59 1999/04/04 21:46:24 dt Exp $
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# $Id: Makefile.inc,v 1.60 1999/04/05 07:38:07 bde Exp $
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# sys sources
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.PATH: ${.CURDIR}/../libc/${MACHINE_ARCH}/sys ${.CURDIR}/../libc/sys
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@ -124,7 +124,7 @@ MLINKS+=lseek.2 seek.2
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MLINKS+=mlock.2 munlock.2
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MLINKS+=mount.2 unmount.2
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MLINKS+=pathconf.2 fpathconf.2
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MLINKS+=read.2 readv.2
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MLINKS+=read.2 pread.2 read.2 readv.2
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MLINKS+=recv.2 recvfrom.2 recv.2 recvmsg.2
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MLINKS+=send.2 sendmsg.2 send.2 sendto.2
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MLINKS+=setpgid.2 setpgrp.2
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@ -135,7 +135,7 @@ MLINKS+=statfs.2 fstatfs.2
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MLINKS+=syscall.2 __syscall.2
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MLINKS+=truncate.2 ftruncate.2
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MLINKS+=wait.2 wait3.2 wait.2 wait4.2 wait.2 waitpid.2
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MLINKS+=write.2 writev.2
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MLINKS+=write.2 pwrite.2 write.2 writev.2
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.if !defined(NO_P1003_1B)
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MLINKS+=sched_get_priority_max.2 sched_get_priority_min.2 \
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sched_get_priority_max.2 sched_rr_get_interval.2
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@ -36,7 +36,8 @@
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.Os BSD 4
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.Sh NAME
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.Nm read ,
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.Nm readv
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.Nm readv ,
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.Nm pread
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.Nd read input
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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@ -46,6 +47,8 @@
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.Fn read "int d" "void *buf" "size_t nbytes"
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.Ft ssize_t
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.Fn readv "int d" "const struct iovec *iov" "int iovcnt"
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.Ft ssize_t
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.Fn pread "int d" "void *buf" "size_t nbytes" "off_t offset"
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.Sh DESCRIPTION
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.Fn Read
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attempts to read
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@ -61,6 +64,9 @@ into the
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buffers specified by the members of the
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.Fa iov
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array: iov[0], iov[1], ..., iov[iovcnt\|\-\|1].
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.Fn Pread
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performs the same function, but reads from the specified position in
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the file without modifying the file pointer.
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.Pp
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For
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.Fn readv ,
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@ -99,9 +105,10 @@ position. The value of the pointer associated with such an
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object is undefined.
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.Pp
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Upon successful completion,
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.Fn read
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.Fn read ,
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.Fn readv ,
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and
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.Fn readv
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.Fn pread
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return the number of bytes actually read and placed in the buffer.
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The system guarantees to read the number of bytes requested if
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the descriptor references a normal file that has that many bytes left
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@ -162,9 +169,10 @@ Otherwise, a -1 is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Fn Read
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.Fn Read ,
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.Fn readv ,
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and
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.Fn readv
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.Fn pread
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will succeed unless:
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.Bl -tag -width Er
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.It Bq Er EBADF
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@ -211,6 +219,16 @@ Part of the
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.Fa iov
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points outside the process's allocated address space.
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.El
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.Pp
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The
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.Fn pread
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call may also return the following errors:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The specified file offset is invalid.
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.It Bq Er ESPIPE
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The file descriptor is associated with a pipe, socket, or FIFO.
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.El
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.Sh SEE ALSO
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.Xr dup 2 ,
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.Xr fcntl 2 ,
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@ -224,8 +242,19 @@ The
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.Fn read
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function call is expected to conform to
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.St -p1003.1-90 .
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The
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.Fn readv
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and
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.Fn pread
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functions are expected to conform to
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.St -xpg4.2 .
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.Sh HISTORY
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The
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.Fn pread
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function call
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appeared in
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.At V.4 .
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The
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.Fn readv
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function call
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appeared in
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@ -36,7 +36,8 @@
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.Os BSD 4
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.Sh NAME
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.Nm write ,
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.Nm writev
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.Nm writev ,
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.Nm pwrite
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.Nd write output
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.Sh SYNOPSIS
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.Fd #include <sys/types.h>
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@ -46,6 +47,8 @@
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.Fn write "int d" "const void *buf" "size_t nbytes"
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.Ft ssize_t
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.Fn writev "int d" "const struct iovec *iov" "int iovcnt"
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.Ft ssize_t
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.Fn pwrite "int d" "const void *buf" "size_t nbytes" "off_t offset"
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.Sh DESCRIPTION
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.Fn Write
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attempts to write
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@ -61,6 +64,9 @@ from the
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buffers specified by the members of the
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.Fa iov
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array: iov[0], iov[1], ..., iov[iovcnt\|-\|1].
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.Fn Pwrite
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performs the same function, but writes to the specified position in
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the file without modifying the file pointer.
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.Pp
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For
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.Fn writev ,
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@ -168,9 +174,10 @@ is returned. Otherwise a -1 is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Fn Write
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.Fn Write ,
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.Fn writev ,
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and
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.Fn writev
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.Fn pwrite
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will fail and the file pointer will remain unchanged if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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@ -229,6 +236,16 @@ values in the
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.Fa iov
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array overflowed a 32-bit integer.
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.El
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.Pp
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The
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.Fn pwrite
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call may also return the following errors:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The specified file offset is invalid.
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.It Bq Er ESPIPE
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The file descriptor is associated with a pipe, socket, or FIFO.
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.El
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.Sh SEE ALSO
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.Xr fcntl 2 ,
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.Xr lseek 2 ,
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@ -240,8 +257,19 @@ The
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.Fn write
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function call is expected to conform to
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.St -p1003.1-90 .
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The
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.Fn writev
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and
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.Fn pwrite
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functions are expected to conform to
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.St -xpg4.2 .
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.Sh HISTORY
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The
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.Fn pwrite
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function call
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appeared in
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.At V.4 .
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The
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.Fn writev
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function call
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appeared in
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