windows - 使用批处理文件插入字符串

Question

我想用批处理文件插入一个字符串来替换特定列中的空白区域假设我有一个 input.txt 如下所示

field1      field2           field3
AAAAA       BBBBB            CCCCC
DDDDD                        EEEEE
FFFFF                        
GGGGG       HHHHH 

我需要在每个空字段上插入一个字符串“NULL”，并确保字段 1 不为空并且 field 2,3 有时会为空。另外，field1 &field2 和field2 & field 3 之间的空格是不一样的

输出.txt

field1      field2           field3
AAAAA       BBBBB            CCCCC
DDDDD       NULL             EEEEE
FFFFF       NULL             NULL    
GGGGG       HHHHH            NULL

因为我仍然需要批处理文件脚本..我尝试编写代码(字段 2 始终从左起 12 个字符开始，字段 3 始终从左起 29 个字符开始)

@echo off

set line= 
for /F in (input.txt)do
if "!line:~12" equ " " 
write "NULL"   >> (i am not sure whether this work)

if "!line:~29" equ " "
write "NULL"  

echo .>> output.txt

也许，有人可以纠正我的错误吗？谢谢!!

Answer 1

正如所 promise 的，这是 Python 中的解决方案。该程序可以与 Python 3.x 或 Python 2.7 一起正常工作。如果您是编程新手，我建议您使用 Python 3.x，因为我认为它更容易学习。您可以从这里免费获得 Python:http://python.org/download/

Python最新版本是3.2.3版本；我建议你明白这一点。

将 Python 代码保存在名为 add_null.py 的文件中，然后使用以下命令运行它:

python add_null.py input_file.txt output_file.txt

代码，有很多注释:

# import brings in "modules" which contain extra code we can use.
# The "sys" module has useful system stuff, including the way we can get
# command-line arguments.
import sys

# sys.argv is an array of command-line arguments.  We expect 3 arguments:
# the name of this program (which we don't care about), the input file
# name, and the output file name.
if len(sys.argv) != 3:
    # If we didn't get the right number of arguments, print a message and exit.
    print("Usage: python add_null.py <input_file> <output_file>")
    sys.exit(1)

# Unpack the arguments into variables.  Use '_' for any argument we don't
# care about.
_, input_file, output_file = sys.argv


# Define a function we will use later.  It takes two arguments, a string
# and a width.
def s_padded(s, width):
    if len(s) >= width:
        # if it is already wide enough, return it unchanged
        return s
    # Not wide enough!  Figure out how many spaces we need to pad it.
    len_padding = width - len(s)
    # Return string with spaces appended.  Use the Python "string repetition"
    # feature to repeat a single space, len_padding times.
    return s + ' ' * len_padding


# These are the column numbers we will use for splitting, plus a width.
# Numbers put together like this, in parentheses and separated by commas,
# are called "tuples" in Python.  These tuples are: (low, high, width)
# The low and high numbers will be used for ranges, where we do use the
# low number but we stop just before the high number.  So the first pair
# will get column 0 through column 11, but will not actually get column 12.
# We use 999 to mean "the end of the line"; if the line is too short, it will
# not be an error.  In Python "slicing", if the full slice can't be done, you
# just get however much can be done.
#
# If you want to cut off the end of lines that are too long, change 999 to
# the maximum length you want the line ever to have.  Longer than
# that will be chopped short by the "slicing".
#
# So, this tells the program where the start and end of each column is, and
# the expected width of the column.  For the last column, the width is 0,
# so if the last column is a bit short no padding will be added.  If you want
# to make sure that the lines are all exactly the same length, change the
# 0 to the width you want for the last column.
columns = [ (0, 12, 12), (12, 29, 17), (29, 999, 0) ]
num_columns = len(columns)

# Open input and output files in text mode.
# Use a "with" statement, which will close the files when we are done.
with open(input_file, "rt") as in_f, open(output_file, "wt") as out_f:
    # read the first line that has the field headings
    line = in_f.readline()
    # write that line to the output, unchanged
    out_f.write(line)

    # now handle each input line from input file, one at a time
    for line in in_f:
        # strip off only the line ending
        line = line.rstrip('\n')

        # start with an empty output line string, and append to it
        output_line = ''
        # handle each column in turn
        for i in range(num_columns):
            # unpack the tuple into convenient variables
            low, high, width = columns[i]
            # use "slicing" to get the columns we want
            field = line[low:high]
            # Strip removes spaces and tabs; check to see if anything is left.
            if not field.strip():
                # Nothing was left after spaces removed, so put "NULL".
                field = "NULL"

            # Append field to output_line.  field is either the original
            # field, unchanged, or else it is a "NULL".  Either way,
            # append it.  Make sure it is the right width.
            output_line += s_padded(field, width)

        # Add a line ending to the output line.
        output_line += "\n"
        # Write the output line to the output file.
        out_f.write(output_line)

运行这个程序的输出:

field1      field2           field3
AAAAA       BBBBB            CCCCC
DDDDD       NULL             EEEEE
FFFFF       NULL             NULL
GGGGG       HHHHH            NULL