First: `man find` shows there are options for "UNUSUAL FILENAMES" (e.g. filenames with spaces).
Code:
-print0
This working depends on the find-command you have supporting it. Actually -print0 is a GNU-extension and, for instance, the find on AIX doesn't know it.
To the rest of your sentiments, though, i can wholeheartedly agree.
[..]Second: using a "for loop" may be dangerous, there can be more results than a Unix line can handle. [..]
Hi Ivo, this is not correct, there are no line length limitations to a for loop, which is part of the shell syntax, so the limitations of passing parameters to a subprocess do not apply.
The problem with the construct in post #1 is that the result of the command substitution (`...`) is vulnerable to interpretation by the shell, e.g. field splitting, so for example files with spaces will be split in two or more arguments and these arguments typically do not exist and so this will fail, hence the (No such file or directory) messages..
Last edited by Scrutinizer; 07-21-2016 at 08:29 AM..
there are no line length limitations to a for loop, which is part of the shell syntax, so the limitations of passing parameters to a subprocess do not apply
Yes - and No: the maximum number of passed arguments will not apply but the maximum line length will. Suppose you have a line like:
Code:
for x in * [; do ....]
and you execute that in a directory with really many files, it will first be expanded by the shell to:
Code:
for x in fileA fileB fileC [...]
and if the really many filenames make this line too long for the shells input parser to fathom you will be in deep kimchi. I give you that: some shells don't care for system constants like "LINE_MAX", but as far as i know a POSIXly correct utility has only to be able to digest lines up to that length. Above that all bets are off. So, if you want to stay on the safe side you better do not require something that is optional in the standards.
From /usr/include/sys/limits.h on a rather up-to-date AIX 7.1-system:
Code:
/* The system supports the following utility limit minimum values */
#define _POSIX2_BC_BASE_MAX 99 /* max ibase and obase values for bc */
#define _POSIX2_BC_DIM_MAX 2048 /* max num elements in array for bc */
#define _POSIX2_BC_SCALE_MAX 99 /* max scale value allowed by bc */
#define _POSIX2_BC_STRING_MAX 1000 /* max len of string constant by bc */
#define _POSIX2_EQUIV_CLASS_MAX 2 /* this define is obsolete */
#define _POSIX2_COLL_WEIGHTS_MAX 2 /* max num weight for LC_COLLATE order */
#define _POSIX2_EXPR_NEST_MAX 32 /* max num expression nested for expr */
#define _POSIX2_LINE_MAX 2048 /* max len of utility input line */
#define _POSIX2_RE_DUP_MAX 255 /* max num repeated reg for interval not */
Yes - and No: the maximum number of passed arguments will not apply but the maximum line length will. Suppose you have a line like:
Code:
for x in * [; do ....]
and you execute that in a directory with really many files, it will first be expanded by the shell to:
Code:
for x in fileA fileB fileC [...]
and if the really many filenames make this line too long for the shells input parser to fathom you will be in deep kimchi.
Yes, the shell expands the wild card, but it does not somehow pass the expanded result as an input line to itself, it does not pass anything. It would only do that if it would pass it to another process, but it does not do that here.
Quote:
I give you that: some shells don't care for system constants like "LINE_MAX", but as far as i know a POSIXly correct utility has only to be able to digest lines up to that length. Above that all bets are off. So, if you want to stay on the safe side you better do not require something that is optional in the standards.
From /usr/include/sys/limits.h on a rather up-to-date AIX 7.1-system:
Code:
[..]
#define _POSIX2_LINE_MAX 2048 /* max len of utility input line */
[..]
[..]
A for loop is not a utility! It is part of the shell syntax, it is not even a builtin utility. So LINE_MAX does not play a role either!
I'm making a shell script to:
-copy directories to a new location
-perform conversions on the files within the copied directories
-move the newly created files to a new directory
Please see my super basic script and notes below... and thank you thank you thank you in advance !!
... (1 Reply)
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folder name is "October Scripts"
I am currently storing the name of folder in a shell variable as so path="October\ Scripts/".
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What am I doing wrong?
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alias
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Hi,
I did the following script:
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This code do the following actions:
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Hi Gurus,
I have a requirement.
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sed 's/*|*/|/g' |
sed 's/^*//'|
sed 's/^*//;
s/*$//' > temp.txt
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Hi,
What's the best way to find all files under a directory - including ones with space - in order to apply a command to each of them. For instance I want get a list of files under a directory and generate a checksum for each file.
Here's the csh script:
#!/bin/csh
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Hi Unix Guru's,
I have encountered a strange problem with doing a restore on a local sunu machine.
We have 2 live system (v880, v450) and 1 test system v440.
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The script below was written to select files and convert a particular string to something other and replace that file. However, I came across some issues with filenames that contain spaces, any suggestions to get around this? Any other suggestions that may apply to this code would also be... (5 Replies)
