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  1. Unison Kernel
    1. Pthreads
      1. pthread_create()
      2. pthread_exit()
      3. pthread_self()
      4. pthread_equal()
      5. pthread_join()
      6. pthread_detach()
      7. pthread_setschedparam()
      8. pthread_getschedparam()
      9. pthread_attr_init()
      10. pthread_attr_destroy()
      11. pthread_attr_setstackaddr()
      12. pthread_attr_getstackaddr()
      13. pthread_attr_setstacksize()
      14. pthread_attr_getstacksize()
      15. pthread_attr_setschedparam()
      16. pthread_attr_getschedparam()
      17. pthread_attr_setdetachstate()
      18. pthread_attr_getdetachstate()
      19. pthread_stackinfo()
      20. pthread_setprio()
      21. pthread_getprio()
      22. sched_get_priority_max()
      23. sched_get_priority_min()
      24. sched_yield()
    2. Pthread Cancellation
      1. pthread_cleanup_pop()
      2. pthread_cleanup_push()
      3. pthread_cancel()
      4. pthread_setcanceltype()
      5. pthread_setcancelstate()
      6. pthread_testcancel()
    3. Mutex
      1. pthread_mutex_init()
      2. pthread_mutex_destroy()
      3. pthread_mutex_lock()
      4. pthread_mutex_trylock()
      5. pthread_mutex_unlock()
    4. Semaphores
      1. sem_open()
      2. sem_close()
      3. sem_unlink()
      4. sem_init()
      5. sem_destroy()
      6. sem_wait()
      7. sem_trywait()
      8. sem_timedwait()
      9. sem_post()
      10. sem_getvalue()
    5. Message Queues
      1. mq_open()
      2. mq_close()
      3. mq_unlink()
      4. mq_send()
      5. mq_receive()
      6. mq_notify()
      7. mq_setattr()
      8. mq_getattr()
      9. mq_timedreceive()
      10. mq_timedsend()
    6. Conditional Variables
      1. pthread_cond_init()
      2. pthread_cond_destroy()
      3. pthread_cond_wait()
      4. pthread_cond_timedwait()
      5. pthread_cond_signal()
      6. pthread_cond_broadcast()
      7. pthread_condattr_init()
      8. pthread_condattr_destroy()
    7. Barriers
      1. pthread_barrier_init()
      2. pthread_barrier_destroy()
      3. pthread_barrier_wait()
    8. Timers
      1. timer_create()
      2. timer_delete()
      3. timer_settime()
      4. timer_gettime()
      5. timer_getoverrun()
      6. timer_tick()
      7. nanosleep()
    9. Clocks
      1. time()
      2. uptime()
      3. sleep()
      4. clock_settime()
      5. clock_gettime()
      6. clock_getres()
      7. clock_init()
    10. Memory Allocation
      1. POSIX.1
        1. malloc()
        2. free()
      2. Variable Length (Pools)
        1. pool_create()
        2. pool_destroy()
        3. pool_alloc()
        4. pool_free()
      3. Fixed Length (Partitions)
        1. pt_create()
        2. pt_destroy()
        3. pt_getblock()
        4. pt_freeblock()
    11. Rendezvous
      1. mr_init()
      2. mr_send()
      3. mr_receive()
      4. mr_reply()
      5. mr_sigrecv()
      6. mr_sigpost()
    12. Interrupts
      1. interrupts
      2. i_disable()
      3. i_restore()
    13. Directory Services
      1. dir_register()
      2. dir_deregister()
      3. dir_lookup()
      4. dir_lookup_string()
    14. Miscellaneous
      1. checkIstack()
      2. NanoStart() or DSPexec_Start()
      3. _isrStackFill
      4. Kernel Scaling
      5. kfatal()
      6. kalloc()
      7. kfree()
      8. mpu or mmu
      9. pthreadStackFill
      10. thread_numb()
      11. thread_utilization_start()
      12. thread_utilization_stop()
      13. xprintf()
      14. xputs()
      15. xputchar()
  2. Unison I/O Library
    1. accept()
    2. bind()
    3. chmod()
    4. close()
    5. connect()
    6. creat()
    7. fstat()
    8. getpeername()
    9. getsockname()
    10. getsockopt()
    11. ioctl()
    12. link()
    13. listen()
    14. lseek()
    15. mkdir()
    16. mkfs()
    17. mount()
    18. open()
    19. read()
    20. recv()
    21. recvfrom()
    22. rename()
    23. renameat()
    24. rmdir()
    25. select()
    26. send()
    27. sendto()
    28. setsockopt()
    29. shutdown()
    30. socket()
    31. stat()
    32. sync()
    33. umount()
    34. unlink()
    35. write()
  3. Unison STDIO Library
    1. STDIO Library Calls
      1. clearerr()
      2. dprintf()
      3. fclose()
      4. fdopen()
      5. feof()
      6. ferror()
      7. fileno()
      8. fflush()
      9. fgetc()
      10. fgetpos()
      11. fgets()
      12. fopen()
      13. fprintf()
      14. fputc()
      15. fputs()
      16. fread()
      17. freopen()
      18. fscanf()
      19. fseek()
      20. fseeko()
      21. fsetpos()
      22. ftell()
      23. ftello()
      24. fwrite()
      25. getc()
      26. getc_unlocked()
      27. getchar()
      28. getchar_unlocked()
      29. getdelim()
      30. getline()
      31. gets()
      32. get_stderr_ptr()
      33. get_stdin_ptr()
      34. get_stdout_ptr()
      35. noperprintf()
      36. perprintf()
      37. perror()
      38. posix_compat()
      39. printf()
      40. putc()
      41. putc_unlocked()
      42. putchar()
      43. putchar_unlocked()
      44. puts()
      45. remove()
      46. rewind()
      47. scanf()
      48. setbuf()
      49. setvbuf()
      50. snprintf()
      51. sprintf()
      52. sscanf()
      53. stderr_init()
      54. stderr_close()
      55. stdin_init()
      56. stdin_close()
      57. stdout_init()
      58. stdout_close()
      59. vdprintf()
      60. vscanf()
      61. vsscanf()
      62. vfscanf()
      63. vprintf()
      64. vsnprintf()
      65. vsprintf()
      66. vfprintf()
      67. ungetc()
    2. Do-nothing Stubs
      1. ctermid()
      2. flockfile()
      3. fmemopen()
      4. ftrylockfile()
      5. open_memstream()
      6. pclose()
      7. popen()
      8. tempnam()
      9. tmpfile()
      10. tmpnam()
  4. Unison LIBC Library
    1. LIBC Library Calls
      1. assert()
      2. realloc()
      3. strcasecmp()
      4. strdup()
      5. strncasecmp()
      6. strftime()
    2. Do-nothing Stubs
      1. abort()
      2. execve()
      3. exit()
      4. _Exit()
      5. fork()
      6. getpid()
      7. isatty()
      8. kill()
      9. sbrk()
      10. times()
      11. wait()
    3. Do-nothing Wide-character Stubs
      1. <wchar.h>
      2. <wctype.h>
  5. Unison I/O Servers
    1. File Servers
      1. Multimedia File Server - fsys
      2. FAT File System - fatfs
      3. NAND File Server - nandfsys
      4. NOR File Server - norfsys
      5. Network File Server - nfs
  6. Graphics, Camera, Video, Audio
    1. Vendor Graphics
    2. Prism++ Graphics
    3. ADPCM Services - adpcmd
    4. Camera
  7. Network Protocols
    1. TCP and UDP Server - tcpd
      1. IPv4 only server
      2. IPv4/IPv6 server
    2. DHCP Client Service - dhcp client
    3. DHCP Server - dhcpd
    4. Telnet Server - telnetd
    5. Tiny FTP Server - tftpd
    6. Point to Point - pppd
    7. Network Translation - NAT with PAT
    8. Firewall
      1. Packet filter: pf
      2. Packet filter control: pfctl
      3. Fitler rules: pf.filtering
      4. Translation rules: pf.nat
    9. Tiny HTTP Server - thttpd
    10. Tiny HTTP Server with TLS
    11. POP3 Server
    12. Simple Mail Transfer Protocol Services (SMTP)
    13. Bootp Protocol
    14. File Transfer Protocol Server (FTP)
    15. File Transfer Client Services
    16. RPC / XDR
    17. DNS Client
    18. HTTP/HTTPS Client
    19. REST Client
    20. AutoIP Service - autoip client
    21. mDNS server - mdnsd
    22. SNTP Client
    23. SNMP Agent - Snmpd server
    24. SSL/TLS library
    25. SSH server
    26. IP security
      1. IPsec description
      2. IPsec administration: ipsecadm
      3. Virtual Private Network: VPN
    27. Power Control
      1. Motor and Motion Control Servers
      2. PWM, Encoders
    28. Serial I/O
      1. Asynchronous Serial I/O Server - ttyserver
      2. CAN Server - cand
      3. I2C Server - i2cd
      4. I2S Server - i2sd
    29. System Services
      1. Power Management Servers
      2. Login Service - login_services
      3. XML
      4. POSIX Shell and Login Service - posh
    30. Universal Serial Bus (USB)
      1. USB Server
      2. USB Device Server
      3. USB Embedded Host Server
    31. Wireless
      1. Wireless Servers and Drivers
      2. 802.15.4 Radio Servers
      3. TCP/v6 with 6loWPAN
      4. ZigBee
      5. BlueTooth Server
      6. 802.11 Wi-Fi
      7. GPRS, UHF and GPS Radio Servers
    32. Remedy Tools for Unison
      1. Remedy Data Logging and Event Display Tools
      2. Remedy Diagnostics
      3. Remedy Flash Downloader/Bootloader
      4. Remedy Power On Self Test - POST
      5. Remedy OS Object Viewer
      6. Remedy Remote Control Tools

2.14.lseek() #

NAME

lseek – move read/write file pointer

SYNOPSIS

#include <sys/types.h>
#include <unistd.h>

off_t lseek(int fildes , off_t offset , int whence );

DESCRIPTION

lseek() sets the file pointer associated with the open file descriptor specified by fildes as follows: If whence is

SEEK_SET
The pointer is set to offset bytes.
SEEK_CUR
The pointer is set to its current location plus offset.
SEEK_END
The pointer is set to the size of the file plus offset.

On success, lseek() returns the resulting pointer location, as measured in bytes from the beginning of the file. Note that if fildes is a remote file descriptor and offset is negative, lseek() returns the file pointer even if it is negative.

lseek() allows the file pointer to be set beyond the existing data in the file. If data are later written at this point, subsequent reads in the gap between the previous end of data and the newly written data will return bytes of value 0 until data are written into the gap.

RETURN VALUES

Upon successful completion, the resulting file pointer is returned. Remote file descriptors are the only ones that allow negative file pointers. Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS

This function is a member of Unison’s IOLIB family of functions. IOLIB is implemented as a message passing and generalized interface layer. Each Unison I/O server is responsible for its own error reporting.

For an exact list of error codes returned by a particular server, refer to that server’s documentation in the Unison Programmer’s Guide for each specific platform.

Servers may implement these errors codes in response to this function.

lseek() fails and the file pointer remains unchanged if one or more of the following are true:

EBADF
fildes is not an open file descriptor.
ENOTSUPPORTED
Operation is not permitted on fildes.
EINVAL
whence is not SEEK_SET, SEEK_CUR, or SEEK_END. Or, the resulting file pointer would be negative.
ESPIPE
fildes is associated with a socket.

Some devices are incapable of seeking. The value of the file pointer associated with such a device is undefined.

SEE ALSO

open(), read(), write() , fseek()

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