Linux command like cat to read a specified quantity of characters

Question

Is there a command like cat in linux which can return a specified quantity of characters from a file   e g   I have a text file like   Hello world this is the second line this is the third line   And I want something that would return the first 5 characters  which would be  hello    thanks

User · Answer

You can use dd to extract arbitrary chunks of bytes.

For example,

dd skip=1234 count=5 bs=1

would copy bytes 1235 to 1239 from its input to its output, and discard the rest.

To just get the first five bytes from standard input, do:

dd count=5 bs=1

Note that, if you want to specify the input file name, dd has old-fashioned argument parsing, so you would do:

dd count=5 bs=1 if=filename

Note also that dd verbosely announces what it did, so to toss that away, do:

dd count=5 bs=1 2>&-

or

dd count=5 bs=1 2>/dev/null

User · Answer

head works too   head -c 100 file    returns the first 100 bytes in the file     will extract the first 100 bytes and return them    What s nice about using head for this is that the syntax for tail matches   tail -c 100 file    returns the last 100 bytes in the file   You can combine these to get ranges of bytes  For example  to get the second 100 bytes from a file  read the first 200 with head and use tail to get the last 100   head -c 200 file   tail -c 100

User · Answer

head works too   head -c 100 file    returns the first 100 bytes in the file     will extract the first 100 bytes and return them    What s nice about using head for this is that the syntax for tail matches   tail -c 100 file    returns the last 100 bytes in the file   You can combine these to get ranges of bytes  For example  to get the second 100 bytes from a file  read the first 200 with head and use tail to get the last 100   head -c 200 file   tail -c 100

User · Answer

Even though this was answered accepted years ago  the presently accepted answer is only correct for one-byte-per-character encodings like iso-8859-1  or for the single-byte subsets of variable-byte character sets  like Latin characters within UTF-8   Even using multiple-byte splices instead would still only work for fixed-multibyte encodings like UTF-16  Given that now UTF-8 is well on its way to being a universal standard  and when looking at this list of languages by number of native speakers and this list of top 30 languages by native secondary usage  it is important to point out a simple variable-byte character-friendly  not byte-based  technique  using cut -c and tr sed with character-classes   Compare the following which doubly fails due to two common Latin-centric mistakes presumptions regarding the bytes vs  characters issue  one is head vs  cut  the other is  a-z  A-Z  vs    upper    lower        printf        p     a       sa s   t     n            head -c 1           sed -e  s  A-Z   a-z  g    unreadable binary mess  or nothing if the terminal filtered it     to this  note  this worked fine on FreeBSD  but both cut  amp  tr on GNU Linux still mangled Greek in UTF-8 for me though      printf        p     a       sa s   t     n            cut -c 1           tr    upper       lower    p      Another more recent answer had already proposed  cut   but only because of the side issue that it can be used to specify arbitrary offsets  not because of the directly relevant character vs  bytes issue    If your cut doesn t handle -c with variable-byte encodings correctly  for  the first X characters   replace X with your number  you could try    sed -E -e  1 s     X       1   -e q - which is limited to the first line though head -n 1   grep -E -o     X   - which is limited to the first line and chains two commands though dd - which has already been suggested in other answers  but is really cumbersome A complicated sed script with sliding window buffer to handle characters spread over multiple lines  but that is probably more cumbersome fragile than just using something like dd   If your tr doesn t handle character-classes with variable-byte encodings correctly you could try    sed -E -e  s    upper     L amp  g  GNU-specific

User · Answer

Even though this was answered accepted years ago  the presently accepted answer is only correct for one-byte-per-character encodings like iso-8859-1  or for the single-byte subsets of variable-byte character sets  like Latin characters within UTF-8   Even using multiple-byte splices instead would still only work for fixed-multibyte encodings like UTF-16  Given that now UTF-8 is well on its way to being a universal standard  and when looking at this list of languages by number of native speakers and this list of top 30 languages by native secondary usage  it is important to point out a simple variable-byte character-friendly  not byte-based  technique  using cut -c and tr sed with character-classes   Compare the following which doubly fails due to two common Latin-centric mistakes presumptions regarding the bytes vs  characters issue  one is head vs  cut  the other is  a-z  A-Z  vs    upper    lower        printf        p     a       sa s   t     n            head -c 1           sed -e  s  A-Z   a-z  g    unreadable binary mess  or nothing if the terminal filtered it     to this  note  this worked fine on FreeBSD  but both cut  amp  tr on GNU Linux still mangled Greek in UTF-8 for me though      printf        p     a       sa s   t     n            cut -c 1           tr    upper       lower    p      Another more recent answer had already proposed  cut   but only because of the side issue that it can be used to specify arbitrary offsets  not because of the directly relevant character vs  bytes issue    If your cut doesn t handle -c with variable-byte encodings correctly  for  the first X characters   replace X with your number  you could try    sed -E -e  1 s     X       1   -e q - which is limited to the first line though head -n 1   grep -E -o     X   - which is limited to the first line and chains two commands though dd - which has already been suggested in other answers  but is really cumbersome A complicated sed script with sliding window buffer to handle characters spread over multiple lines  but that is probably more cumbersome fragile than just using something like dd   If your tr doesn t handle character-classes with variable-byte encodings correctly you could try    sed -E -e  s    upper     L amp  g  GNU-specific

User · Answer

head   Name  head - output the first part of files  Synopsis  head  OPTION      FILE      Description  Print the first 10 lines of each FILE to standard output  With more than one FILE  precede each with a header giving the file name  With no FILE  or when FILE is -  read standard input  Mandatory arguments to long options are mandatory for short options too   -c  --bytes  - N print the first N bytes of each file  with the leading  -   print all but the last N bytes of each file

User · Answer

head works too   head -c 100 file    returns the first 100 bytes in the file     will extract the first 100 bytes and return them    What s nice about using head for this is that the syntax for tail matches   tail -c 100 file    returns the last 100 bytes in the file   You can combine these to get ranges of bytes  For example  to get the second 100 bytes from a file  read the first 200 with head and use tail to get the last 100   head -c 200 file   tail -c 100

User · Answer

head   Name  head - output the first part of files  Synopsis  head  OPTION      FILE      Description  Print the first 10 lines of each FILE to standard output  With more than one FILE  precede each with a header giving the file name  With no FILE  or when FILE is -  read standard input  Mandatory arguments to long options are mandatory for short options too   -c  --bytes  - N print the first N bytes of each file  with the leading  -   print all but the last N bytes of each file

User · Answer

head or tail can do it as well    head -c X   Prints the first X bytes  not necessarily characters if it s a UTF-16 file  of the file  tail will do the same  except for the last X bytes   This  and cut  are portable

User · Answer

head   Name  head - output the first part of files  Synopsis  head  OPTION      FILE      Description  Print the first 10 lines of each FILE to standard output  With more than one FILE  precede each with a header giving the file name  With no FILE  or when FILE is -  read standard input  Mandatory arguments to long options are mandatory for short options too   -c  --bytes  - N print the first N bytes of each file  with the leading  -   print all but the last N bytes of each file

User · Answer

head or tail can do it as well    head -c X   Prints the first X bytes  not necessarily characters if it s a UTF-16 file  of the file  tail will do the same  except for the last X bytes   This  and cut  are portable

User · Answer

you could also grep the line out and then cut it like for instance   grep  text  filename   cut -c 1-5

User · Answer

you could also grep the line out and then cut it like for instance   grep  text  filename   cut -c 1-5

User · Answer

head   Name  head - output the first part of files  Synopsis  head  OPTION      FILE      Description  Print the first 10 lines of each FILE to standard output  With more than one FILE  precede each with a header giving the file name  With no FILE  or when FILE is -  read standard input  Mandatory arguments to long options are mandatory for short options too   -c  --bytes  - N print the first N bytes of each file  with the leading  -   print all but the last N bytes of each file

User · Answer

head works too   head -c 100 file    returns the first 100 bytes in the file     will extract the first 100 bytes and return them    What s nice about using head for this is that the syntax for tail matches   tail -c 100 file    returns the last 100 bytes in the file   You can combine these to get ranges of bytes  For example  to get the second 100 bytes from a file  read the first 200 with head and use tail to get the last 100   head -c 200 file   tail -c 100

User · Answer

You can use dd to extract arbitrary chunks of bytes.

For example,

dd skip=1234 count=5 bs=1

would copy bytes 1235 to 1239 from its input to its output, and discard the rest.

To just get the first five bytes from standard input, do:

dd count=5 bs=1

Note that, if you want to specify the input file name, dd has old-fashioned argument parsing, so you would do:

dd count=5 bs=1 if=filename

Note also that dd verbosely announces what it did, so to toss that away, do:

dd count=5 bs=1 2>&-

or

dd count=5 bs=1 2>/dev/null

User · Answer

head -Line number file name   tail -1  cut -c Num of chars   this script gives the exact number of characters from the specific line and location  e g     head -5 tst txt   tail -1  cut -c 5-8   gives the chars in line 5 and chars 5 to 8 of line 5    Note  tail -1 is used to select the last line displayed by the head

User · Answer

head or tail can do it as well    head -c X   Prints the first X bytes  not necessarily characters if it s a UTF-16 file  of the file  tail will do the same  except for the last X bytes   This  and cut  are portable

User · Answer

Here s a simple script that wraps up using the dd approach mentioned here  extract chars sh    usr bin env bash  function show help       IT  quot  extracts characters X to Y from stdin or FILE usage  X Y  FILE   e g    2 10  tmp it       gt  extract chars 2-10 from  tmp it EOF    quot    echo  quot  IT quot    exit    if    quot  1 quot      quot help quot    then   show help fi if   -z  quot  1 quot    then   show help fi  FROM  1 TO  2 COUNT  expr  TO -  FROM   1   if   -z  quot  3 quot    then   dd skip  FROM count  COUNT bs 1 2 gt  dev null else   dd skip  FROM count  COUNT bs 1 if  3 2 gt  dev null  fi

User · Answer

I know the answer is in reply to a question asked 6 years ago      But I was looking for something similar for a few hours and then found out that  cut -c does exactly that  with an added bonus that you could also specify an offset   cut -c 1-5  will return Hello and cut -c 7-11  will return world  No need for any other command

User · Answer

head -Line number file name   tail -1  cut -c Num of chars   this script gives the exact number of characters from the specific line and location  e g     head -5 tst txt   tail -1  cut -c 5-8   gives the chars in line 5 and chars 5 to 8 of line 5    Note  tail -1 is used to select the last line displayed by the head

User · Answer

you could also grep the line out and then cut it like for instance   grep  text  filename   cut -c 1-5

User · Answer

Here s a simple script that wraps up using the dd approach mentioned here  extract chars sh    usr bin env bash  function show help       IT  quot  extracts characters X to Y from stdin or FILE usage  X Y  FILE   e g    2 10  tmp it       gt  extract chars 2-10 from  tmp it EOF    quot    echo  quot  IT quot    exit    if    quot  1 quot      quot help quot    then   show help fi if   -z  quot  1 quot    then   show help fi  FROM  1 TO  2 COUNT  expr  TO -  FROM   1   if   -z  quot  3 quot    then   dd skip  FROM count  COUNT bs 1 2 gt  dev null else   dd skip  FROM count  COUNT bs 1 if  3 2 gt  dev null  fi

User · Answer

You can use dd to extract arbitrary chunks of bytes.

For example,

dd skip=1234 count=5 bs=1

would copy bytes 1235 to 1239 from its input to its output, and discard the rest.

To just get the first five bytes from standard input, do:

dd count=5 bs=1

Note that, if you want to specify the input file name, dd has old-fashioned argument parsing, so you would do:

dd count=5 bs=1 if=filename

Note also that dd verbosely announces what it did, so to toss that away, do:

dd count=5 bs=1 2>&-

or

dd count=5 bs=1 2>/dev/null

User · Answer

I know the answer is in reply to a question asked 6 years ago      But I was looking for something similar for a few hours and then found out that  cut -c does exactly that  with an added bonus that you could also specify an offset   cut -c 1-5  will return Hello and cut -c 7-11  will return world  No need for any other command

User · Answer

you could also grep the line out and then cut it like for instance   grep  text  filename   cut -c 1-5

User · Answer

head or tail can do it as well    head -c X   Prints the first X bytes  not necessarily characters if it s a UTF-16 file  of the file  tail will do the same  except for the last X bytes   This  and cut  are portable

User · Answer

You can use dd to extract arbitrary chunks of bytes.

For example,

dd skip=1234 count=5 bs=1

would copy bytes 1235 to 1239 from its input to its output, and discard the rest.

To just get the first five bytes from standard input, do:

dd count=5 bs=1

Note that, if you want to specify the input file name, dd has old-fashioned argument parsing, so you would do:

dd count=5 bs=1 if=filename

Note also that dd verbosely announces what it did, so to toss that away, do:

dd count=5 bs=1 2>&-

or

dd count=5 bs=1 2>/dev/null

[linux] Linux command (like cat) to read a specified quantity of characters

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