SHQUOTE(3) | Library Functions Manual | SHQUOTE(3) |
shquote
, shquotev
—
#include <stdlib.h>
size_t
shquote
(const
char *arg, char
*buf, size_t
bufsize);
size_t
shquotev
(int
argc, char * const
*argv, char *buf,
size_t bufsize);
shquote
() and shquotev
()
functions copy strings and transform the copies by adding shell escape and
quoting characters. They are used to encapsulate arguments to be included in
command strings passed to the system
() and
popen
() functions, so that the arguments will have the
correct values after being evaluated by the shell.
The exact method of quoting and escaping may vary, and is intended
to match the conventions of the shell used by
system
() and popen
(). It may
not match the conventions used by other shells. In this implementation, the
following transformation is applied to each input string:
'\''
, andThe shquote
() function transforms the
string specified by its arg argument, and places the
result into the memory pointed to by buf.
The shquotev
() function transforms each of
the argc strings specified by the array
argv independently. The transformed strings are placed
in the memory pointed to by buf, separated by spaces.
It does not modify the pointer array specified by argv
or the strings pointed to by the pointers in the array.
Both functions write up to bufsize - 1
characters of output into the buffer pointed to by
buf, then add a NUL
character
to terminate the output string. If bufsize is given as
zero, the buf parameter is ignored and no output is
written.
shquote
() and shquotev
()
functions return the number of characters necessary to hold the result from
operating on their input strings, not including the terminating
NUL
. That is, they return the length of the string
that would have been written to the output buffer, if it were large enough. If
an error occurs during processing, the value ((size_t)-1) is returned and
errno is set appropriately.
shquotev
() to construct a command string to be used
with system
(). The command uses an environment
variable (which will be expanded by the shell) to determine the actual program
to run. Note that the environment variable may be expanded by the shell into
multiple words. The first word of the expansion will be used by the shell as
the name of the program to run, and the rest will be passed as arguments to
the program.
char **argv, c, *cmd; size_t cmdlen, len, qlen; int argc; ... /* * Size buffer to hold the command string, and allocate it. * Buffer of length one given to snprintf() for portability. */ cmdlen = snprintf(&c, 1, "${PROG-%s} ", PROG_DEFAULT); qlen = shquotev(argc, argv, NULL, 0); if (qlen == (size_t)-1) { ... } cmdlen += qlen + 1; cmd = malloc(cmdlen); if (cmd == NULL) { ... } /* Create the command string. */ len = snprintf(cmd, cmdlen, "${PROG-%s} ", PROG_DEFAULT); qlen = shquotev(argc, argv, cmd + len, cmdlen - len); if (qlen == (size_t)-1) { /* Should not ever happen. */ ... } len += qlen; /* "cmd" can now be passed to system(). */
The following example shows how you would implement the same
functionality using the shquote
() function
directly.
char **argv, c, *cmd; size_t cmdlen, len, qlen; int argc, i; ... /* * Size buffer to hold the command string, and allocate it. * Buffer of length one given to snprintf() for portability. */ cmdlen = snprintf(&c, 1, "${PROG-%s} ", PROG_DEFAULT); for (i = 0; i < argc; i++) { qlen = shquote(argv[i], NULL, 0); if (qlen == (size_t)-1) { ... } cmdlen += qlen + 1; } cmd = malloc(cmdlen); if (cmd == NULL) { ... } /* Start the command string with the env var reference. */ len = snprintf(cmd, cmdlen, "${PROG-%s} ", PROG_DEFAULT); /* Quote all of the arguments when copying them. */ for (i = 0; i < argc; i++) { qlen = shquote(argv[i], cmd + len, cmdlen - len); if (qlen == (size_t)-1) { /* Should not ever happen. */ ... } len += qlen; cmd[len++] = ' '; } cmd[--len] = '\0'; /* "cmd" can now be passed to system(). */
system
() and
popen
()) must first be fixed to handle multibyte
characters. When that has been done, these functions can have multibyte
character support enabled.
September 7, 2008 | NetBSD 9.0 |