Python Os.lseek() Method



Python method lseek() sets the current position of file descriptor fd to the given position pos, modified by how.


Following is the syntax for lseek() method:

os.lseek(fd, pos, how)


  • fd − This is the file descriptor, which needs to be processed.
  • pos − This is the position in the file with respect to the given parameter how. You give os.SEEK_SET or 0 to set the position relative to the beginning of the file, os.SEEK_CUR or 1 to set it relative to the current position; os.SEEK_END or 2 to set it relative to the end of the file.
  • how − This is the reference point within the file. os.SEEK_SET or 0 means beginning of the file, os.SEEK_CUR or 1 means the current position and os.SEEK_END or 2 means the end of the file.

Return Value

This method does not return any value.


The following example shows the usage of lseek() method.


import os, sys

# Open a file
fd = os.open( "foo.txt", os.O_RDWR'os.O_CREAT )

# Write one string
os.write(fd, "This is test")

# Now you can use fsync() method.
# Infact here you would not be able to see its effect.

# Now read this file from the beginning
os.lseek(fd, 0, 0)
str = os.read(fd, 100)
print "Read String is : ", str

# Close opened file
os.close( fd )

print "Closed the file successfully!!"

When we run the above program, it produces the following result:

Read String is :  This is test
Closed the file successfully!!

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